Science in Christian Perspective                                                                

Validity of Existing Controlled 
Studies Examining the Psychological Effects of Abortion

Numerous studies have been concerned with the potential psychological sequelae (potential psychological risks) of abortion but conclusions reached are inconsistent. This paper is based on a comprehensive review of studies addressing the question of post-abortion psychological sequelae. Controlled studies were categorized according to research design and then systematically examined for experimental validity. Poor use of methodology and research design surfaced as an explanation for differing conclusions across the literature. As a further means of examining the integrity of comparisons in the literature made between woman having and not having abortions, the maximum likely statistical power was calculated for each controlled study. As a whole, the literature exhibited grossly substandard power characteristics. An effort to isolate the best study to date was made, and a summary of the conclusions from this study is presented. We conclude that the question of psychological sequelae to abortion is not closed.

To determine the level of rigor that exists in the psychological sequelae literature, we have undertaken a review of this literature from a methodological and statistical perspective. To locate articles we have relied upon computer searches of Index Medicus, Psychological Abstracts, Science Citation Index and the National Institute of Mental Health data base in addition to examination of the bibliographies of all articles located. This search yielded over 300 studies; seventy-six were either clinical case studies or experimental research. In turn, these studies were organized into four categories according to research design: case studies (17), controlled studies (14), retrospective-uncontrolled studies (20) and prospective-uncontrolled studies (23). Each of these four types of research designs have strengths and weaknesses, some of which will be described below.

Unfortunately, there are many inconsistencies in the conclusions drawn by the authors of the studies we located. For example, Wallerstein, Kurtz and Bar-Din (1972) found adverse reactions in fifty percent of the cases studied, while Osofsky and Osofsky (1972), in a study published the same year, concluded that there were few, if any, adverse psychological reactions. When results are this varied, both pro-life and prochoice camps are able to find "evidence" to support their position. Under such circumstances, the need to consider the methodological and statistical practices underpinning each study becomes self-evident. A review of the foundations on which the literature rests sometimes can differentiate between studies that can be trusted and those that come to unwarranted conclusions. If severe methodological flaws in the current literature do exist, these inadequacies, not the conclusions reached, should be the focus of attention. Thus, it is the experimental validity rather than the conclusions of existing studies that provide the focus of this paper.

James L. Rogers received his Ph.D. in psychology from Northwestern University, Evanston, Illinois. He presently holds appointments as associate professor at Wheaton College, Wheaton, IL and research associate at the Northwestern University Medical School. James F. Phifer is currently pursuing his doctoral degree in clinical psychology at the University of Louisville, Louisville, KY. Julie A. Nelson received her M.A. in psychological studies from the Wheaton College Graduate School, Wheaton, IL and currently is in private practice.

measure of psychological sequelae). Internal validity refers to the extent to which the observed effects of the outcome variable (psychological sequelae) may be attributed to the treatment (abortion) rather than alternative causes (age, marital status, religious background, etc.). Construct validity pertains to the extent that the outcome measures, treatments, samples and settings utilized in the research represent the theoretical constructs of interest. In the present context, high construct validity would imply (among other things) that the measuring device used to assess risk was reliable and accurate. Finally, external validity refers to the validity with which conclusions can be generalized to and across populations of persons, settings and time. Having high external validity would mean that the conclusions about abortion and psychological risk found in a given study could be safely applied to women other than those actually involved in the study.

A review of the foundations on which the literature rests sometimes can differentiate between studies that can be trusted and those that come to unwarranted conclusions.

We will first discuss statistical conclusion validity as it relates to the post-abortion sequelae literature. There are two types of errors one can make when using a statistical hypothesis test to decide whether an experimental group differs from a control group (i.e., an abortion group differs from a non-abortion control group). Type I error refers to concluding from sample data that there is a difference on the outcome variable (i.e., incidence of psychological trauma) when such is not really the case for the two comparison populations. In effect, you have drawn random samples that look different, but both samples have come from the same population (with regard to the outcome parameter of interest). On the other hand, a Type II error occurs when, on the basis of sample data, it is decided that the samples have come from the same population when really each is from a different population.

Table I
Statistical Power for Fourteen Comparative Studies That Examine the Psychological Sequelae of Abortion

                     Sample Size 
                                                           Harmonic     Relative                          Date
Researcher      N        na     nb               Mean          Power            Country (Data Collected)

David, et al.        98,612  27,234  71,378             39,426                       .99+                                  Denmark 1974-75
Brewer                   7,660    3,550   4,110                3,809                       .99+                                  England 1975-76
Jansson, et al.     30,329   1,773   28,556              3,338                       .99+                                  Sweden 1952-56
Meyerowitz              11l      93       18                         30                        .12                                    U.S.A. 1963-69
Selare, et al.              42       21       21                         21                        .10                                    Scotland 1960-68
Hamill, et al.           128       81       47                         59                         .17                                    Scotland 1971-72
Greenglass,            126      63       63                          63                         .17                                    Canada 1972-73
Niswander,              68      49       19                          27                          .12                                   U.S.A. 1971-72
Athanasiou,         114       76       38                          51                          .16                                   U.S.A. 1970-72
McCance,             300     192    108                        138                           .27                                   Scotland 1967-68
Drower,                 157      88      69                           77                           .19                                   South Africa 1974-75
Brody,                  152      94      58                            72                           .19                                   Canada 1968-70
Simon,                    78      32      46                            38                           .13                                   U.S.A. 1955-63
Todd,                   102       81     22                            35                           .13                                   Scotland 1968-70

Notes: For the purpose of power estimation, we have assumed the following: 1) that "ideal" experimental arrangements exist throughout the literature; namely, that all existing studies perfectly measure an identical outcome parameter that reflects level of depression and that perfect subject equivalency exists at baseline across the two conditions; 2) that post-event depression will be five percent greater in women experiencing abortion than women who carry to term, i.e., that there will be 25% postabortion depression vs. the 20% postpartum depression rate reported by Hopkins, et al., (1984), and 3) that a one tailed z test with alpha set at. 05 on transformed proportions is used as the test statistic.

Power values were determined as outlined by Cohen (1977). In accordance with Cohen's guidelines for unequal sample sizes, the abortion and control group sample sizes (n. and nb, respectively) were converted to a single harmonic mean which was used to enter the power tables.

We do not claim the foregoing argument, but we do maintain that when a large number of individuals believe strongly that a difference between experimental and control groups exists, as is the case in this country regarding the sequelae to abortion question, a statistical decision procedure with good power characteristics (i.e., a low risk of a Type 11 error) must be utilized out of respect for these individuals. In a word, those who are against abortion and believe it to increase psychological sequelae deserve quality studies with good statistical power characteristics. This is true, if for no other reason than that the popular press will label published studies with low statistical power that claim abortion has no psychological effect as "scientific,"and in so doing give them a prestigious status. However, the popular press will not bother to explain, because they will not understand, that there was a good chance of arriving at that conclusion due to limited statistical power, quite aside from whether the conclusion is really true. As scientists who understand these concepts, we have a moral responsibility to make sure that the public is not misled by the absence of "statistically significant" differences in studies with low statistical power.

We have just completed an examination of the existing studies that compare a post-abortion group with a control. After making certain assumptions, we have calculated the level of statistical power present in each study. Our conclusion (see Table 1) is that 11 of the 14 existing studies exhibit statistical power that is not likely to exceed, but could be less than_ 27. We hold that the majority of currently available comparative studies exhibit grossly substandard power characteristics even under assumptions that, if anything, overestimate power levels.

Internal Validity

Internal validity, as noted earlier, refers to the extent to which effects on outcome variables are due to the independent variable (i.e., abortion) rather than to other competing causes. Existing controlled studies addressing the issue of psychological sequelae invariably utilize a quasi-experimerital design, termed the 11 static-group comparison" design in Campbell and Stanley's (1963) classic text, Experimental and Quasiexperimental Designs for Research. (This design is termed the "nonequivalent control group" design if pre-treatment measures are available.) Because it is not possible to randomly assign women to conditions, the abortion and control groups cannot be equated at baseline by chance. Two threats that are endemic to these designs, mortality and selection, will serve to illustrate the serious problems that can plague a study if such threats are not countered.

Selection is a threat when, at the outset of the study, subjects assigned to the experimental condition differ from control subjects on baseline characteristics. In this event, differences or similarities between the experimental and control groups found at the end of the study may be due to the treatment (presence or absence of abortion), one or more baseline differences, or the interaction of the treatment with one or more baseline differences. The threat of selection is usually countered by randomly assigning subjects to conditions, but this, as noted earlier, is impossible for abortion sequelae research. If random assignment cannot be used to equate groups at baseline by chance, then one should at least compare baseline characteristics on selected variables to rule out possible important differences.

Selection was indisputably a potential threat to the internal validity of more than 50 percent of the studies we reviewed because baseline measures simply were not collected. Without carefully establishing the baseline comparability of women who receive an abortion to those who do not on at least such rudimentary characteristics as age, number of children, education, socioeconomic status, social support, marital status and phvsical health, the meaning of differences or similarities in the incidence of sequelae will remain speculative.

Those who are against abortion and believe it to increase psychological sequelae deserve quality studies with good statistical power characteristics.

We would like to illustrate some of the difficulties in the way psychological sequelae have been assessed with some examples. Niswander and Patterson (1967), Ewing and Rouse (1973), Kretzschmar and Norris (1967) and Bracken, Hachamovitch and Grossman (1974) devised their own self-report questionnaires to assess the psychological reaction to abortion. However, in virtually all instances no attempt was made to validate these instruments or even assess their reliability (i.e., consistency and preciseness). A variety of relatively simple methods have been devised for determining reliability (test-retest, parallel forms and split half techniques), but none of these were conducted. Clearly, the use of measuring devices with unknown reliability can potentially distort the conclusions one makes about the psychological impact of abortion.

Other studies have implemented structured or unstructured interviews as the assessment measure (Patt, Rappaport and Barglow, 1969; Wallerstein, Kurtz and Bar-Din, 1972; Osofsky and Osofsky, 1972; Ford, Castelnuovo-Tedesco and Long, 1971; Peck and Marcus, 1966). It is common knowledge that psychiatric interviews can be highly unreliable and are subject to the specific orientation, level of expertise, biases and expectations of the interviewer. In virtually all cases reviewed, no attempt was made to assess inter-rater reliability (the degree to which two interviewers come to similar conclusions about the same subject), or to control for interviewer bias and expectancies. For example, Osofsky and Osofsky (1972) attempted to quantify such behaviors as crying and smiling during an unstructured interview. These behaviors could easily be influenced by characteristics of the interviewer, but no attempt was made to control for such factors.

Without carefully establishing the baseline comparability of women who receive an abortion to those who do not ... the meaning of differences or similarities in the incidence of sequelae will remain speculative.

In general, we found little evidence to suggest that construct validity for the dependent measures used to assess sequelae was at an acceptable level. The list of potential threats to construct validity we found is too great to enumerate in this presentation. However, it includes, in addition to the above problems, such practices as obtaining information concerning the level of emotional adjustment from sources other than the patient (Meyerowitz, Satloff and Romano, 1971; Jacobs, Garcia, Rickels and Preucel, 1974; Pare and Raven, 1970; Lask, 1974); conducting follow-up assessment immediately after the abortion in the recovery room (Braken, Hachamovitch and Grossman, 1974; Osofsky and Osofsky, 1972; Moseley, Follinstad, Harley and Heckel, 1981); interviewing patients at unsystematized follow-up intervals ranging from one to five years (Kretzschmar and Norris, 1967) or several months to seven years (Meyerowitz, Satloff and Romano, 1971); and including patients who not only received an abortion but were also sterilized concomitantly, thus subjecting the subject to two treatments simultaneously and rendering any form of causal interpretation impossible.

External Validity

External validity refers to the ability to generalize findings across populations, settings and time, and is critical if the information is going to be useful apart from its experimental setting. However, the majority of existing studies utilize small, self-selected samples of women who had their abortion at one specific hospital. Such selection bias would likely limit the generalizability of any conclusions reached, even if the conclusions were made under conditions of high internal validity. For example, Niswander and Patterson (1967) asked the attending physician to approve or disapprove the mailing of a questionnaire to each of the patients, thus eliminating those patients of whom it was thought that the recollection of the abortion experience would be too painful. Abrams, DiBiase and Sturgis (1979) sent questionnaires only to those patients whom they felt were likely to respond. In both of these cases, the subject selection procedure could seriously alter the generalizability (external validity) of results.

Generalizability of results would be greatly enhanced if subject selection were stratified across the various settings in which abortions are performed. Indeed, the distribution of such settings can be approximated. In 1982, 82 percent of abortions in America were performed in non-hospital facilities: 56 percent in abortion clinics, 21 percent in other clinics, and 5 percent in physicians' offices (Henshaw, Forrest and Blaine, 1984). Eighteen percent of abortions were performed in hospitals. Unfortunately, no study of which we are aware has attempted to make the research sample utilized in the study representative of have been conducted in the current decade, the research sample utilized in the study representative of these known demographic characteristics. The distribution of settings for the research sample being used is often not even specified

A second obstacle to external validity is highlighted by the widely varying definitions of psychological
sequelae that are used across the various studies in the area. In one respect, the search for abortion related
sequelae of many different kinds enhances generaliz ability. However, to the degree that our confidence in
findings is lessened because results of studies that use different definitions of sequelae are difficult to pool,
generalizability is retarded. This may contribute to the inconsistencies found among results in the literature.
Some studies define negative psychological reactions to abortion in terms of psychological symptornatology
such as depression, anxiety or guilt. Another may attach importance to the number of symptoms, while others
rely on the subjective experience of the woman as she reports it in a self-report questionnaire. The resulting
ambiguities make the literature difficult to summarize as there are no subgroups of studies that consistently
measure the same dependent variable defined in the same way. It therefore goes without saying that the
literature contains few replications of procedures or findings. Given small sample sizes and virtually no
replication across investigators, the potential for non generalizable (not to mention unreliable) conclusions is
substantial.

Clearly, the use of measuring devices with unknown reliability can potentially distort the conclusions one makes about the psychological impact of abortion.

Lastly, generalizability across time is a crucial issue. Approximately half of the studies we reviewed were
conducted from 1967 to 1973 when abortion laws were being liberalized. During this period, therapeutic abor
tions were granted on medical and/or psychiatric grounds. The remaining studies were conducted in the
mid-to-late 1970's under abortion-on-dernand. (Note that some of these studies were not published until the
early 1980's). It is highly questionable as to whether conclusions drawn from studies utilizing women granted abortions on therapeutic grounds only, as was the case until 1973 in the United States, are generalizable to the current social milieu characterized by abortion-on-demand. Furthermore, as no new studies

Generalizability Of results would be greatly enhanced if subject selection were stratified across the various settings in which abortions are performed.

It now should be clear that considerable ambiguity surrounds the question of post-abortion sequelae because numerous methodological problems exist in the literature. In the midst of the confusion arising from generally poor methodology, it is only natural to ask whether some of the existing studies are more trustworthy than others. Certainly when studies of relatively high and low validities conflict, the conclusions of the higher quality studies should be given the most weight. As Mintz (1983) has stated, "literally no number of anecdotal reports, uncontrolled trials or poorly designed experiments can outweigh one carefully planned and executed controlled experiment if it results in clear and divergent findings" (p. 74). On this same issue, Smith, Glass and Miller (1980) write: "The important question in surveying a body of literature is to determine whether the best designed studies yield evidence different from more poorly designed studies. if the answer is yes, then one is compelled to believe the best ones" (p. 64).

Pursuing this line of thought, we would like to critique what we consider to be the "best" study done in this area to date. Danish researchers David, Rasmussen and Holst (1981) have carried out the only study we located that exhibited the minimum criteria of a control group, pretest measures, adequate sample size, an attempt to equate non-equivalent groups at baseline, and assessment tools with adequate validity and reliability. It is our hope that the ensuing critique of this study, which in our opinion is one of the few acceptable studies (but certainly not without problems), will highlight in a concrete way the issues that the clinician and/or woman considering abortion must keep in mind when examining the research.

Utilizing the computer linkage of the Danish national case registry, the above authors studied the

comparative risk of admission to a psychiatric hospital within three months of an abortion or term delivery for all women under age 50 residing in Denmark. Data on admission to psychiatric hospitals was obtained on 71,378 women carrying pregnancies to term, 27,234 women terminating unwanted pregnancies, and on the total population of 1,169,819 women aged 15 to 49. In determining the incidence rates, only first admissions were recorded; women with an admission during the 15 months prior to the delivery or abortion were excluded.

Figure IA contrasts women who delivered, women who had abortions, and all women in Denmark aged 15 through 49 on incidence of psychiatric hospitalization. Incidence rates were highest for women who were post-abortion (18.4 per 10,000), next highest for women who were postpartum (12.0 per 10,000), and lowest for all women (7.5 per 10,000). In Figure 1B the incidence rates have been further broken down by 

age category. Only in women aged 35 through 49 is there a reversal in the direction found in the composite data. Here, women who delivered evidenced a higher rate of psychiatric hospitalization than women who aborted (22.2 per 10,000 vs. 13.4 per 10,000). It appears that the pregnancy event (birth or abortion) interacts with age; women who are post-abortion are at greater risk except in the age category 35 through 49, where the relationship reverses.

Given small sample sizes and virtually no replication across investigators ' the potential for nongeneralizable (not to mention unreliable) conclusions is substantial.

Incidence of psychiatric hospitalization between postpartum and post-abortion women in each of three marital status categories is depicted in 

Figure 1C. Differences across conditions are relatively small for women who were currently married or never were married, but are extreme when considering women who were separated, divorced or widowed (16.9 per 10,000 postpartum vs. 63.8 per 10,000 post-abortion). Apparently, women who have suffered from a separation with their husband also have a more difficult time dealing with the termination of the pregnancy. Lack of an emotional support system may be more prevalent for women who are estranged or whose husbands have died.

Finally, Figure ID compares postpartum and postabortion women across four levels of parity, or number of prior children. Regardless of the number of prior children, women who were postpartum evidenced a lower rate of psychiatric hospitalization than women who were post-abortion. However, these differences are more extreme for women with zero or one prior child (13.8 per 10,000 vs. 22.4 per 10,000 with parity of zero; 9.7 per 10,000 vs. 23.3 per 10,000 with parity of one). This may suggest that women who have one or no offspring are a greater post-abortion psychological risk than those with several children.

Our review of the post-abortion sequelae literature suggests that the majority of studies published in this area are greatly flawed.

Although these findings may seem reasonable to those not acquainted with the post-abortion sequelae literature because they rnirror traditional expectations, it is apparent to anyone who has read this literature that these outcomes stand in stark contrast to conclusions reached by the majority of researchers. The majority of researchers conclude that there is no greater occurrence of post-abortion sequelae than postpartum sequelae. A study representative of this literature was done by the English researcher Brewer (1977) and was published in the prestigious British Medical journal. Brewer places the post-abortion rate at only 3 per 10,000 while the postpartum rate was placed at 17 per 10,000. (See Figure le for a comparison to David, Rasmussen and Hoist). indeed, these findings led Brewer to conclude that " . . . childbirth is more hazardous in psychiatric terms than abortion. . . " (p . 477). However, our analysis indicates that the Danish study by David, Rasmussen and Hoist rests upon a much firmer methodological foundation than does the English study by Brewer.

We would like to delineate some of the problems found in the English study authored by Brewer as an illustration of our concern over poor methodology. First, Brewer relied upon a questionnaire that was sent to psychiatrists in a given British catchment area. Thus, his data depended upon each psychiatrist's memory and/or ability (willingness?) to retrieve records. We know of no reliability or validity coefficients for this questionnaire and have no reason to believe that any were computed. Additionally, the questionnaire was sent to only 25% of the psychiatric consultants in the area. There is no guarantee that these consultants are representative, and indeed Sim and Neisser in their analysis "Post-Abortive Psychoses: A Report from Two Centers" (1979) claim that " . . . the psychiatrist with the greatest responsibility and experience in the area of the assessment and treatment of patients with instability associated with pregnancy did not participate." Brewer also reports that some psychiatric consultants had well defined catchment areas while some had catchment areas that overlapped with those of other psychiatrists. In effect, the result of this overlap was that the denominators in the incidence rates were 11 estimated." All these practices stand in sharp contrast to David, Rasmussen and Holst's use of computer-held data for the entire population of Danish females aged 15 through 49. In addition, the Danish study matches the post-abortion and postpartum conditions on prior incidence of psychiatric admission over the prior 15month period, age, marital status, and parity. No attempt appears to have been made in the English study to equate comparison groups on these or any other factors.

At minimum, the findings of David, Rasmussen, and Holst, with its differing conclusions from studies evidencing less methodological rigor, should underscore the importance of readdressing the issue of postabortion psychological sequelae with better experimental design. Findings reported in what we consider to be the most reliable study to date are compatible with the assertion that post-abortion psychological sequelae occur more frequently than postpartum sequelae. Obviously, it is of considerable importance that other well planned studies be conducted in an effort to verify the findings reported by David, Rasmussen and Holst. It is crucial that these studies move beyond psychiatric hospitalization as an endpoint measurement to include other forms of emotional sequelae. At minimum, depression should be measured.

Our review of the literature leads us to conclude that the questions of psychological sequelae to abortion is not closed as many researchers have stated, but remains to be determined. Although such a conclusion fails to satisfy the expectations of either those for or against abortion on demand, it seems to reflect the present state of affairs.

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30

PERSPECTIVES ON SCIENCE AND CHRISTIAN FAITH

Discovering the truth about the emotional impact of either clinical case studies or experimental research. In
abortion should be of great interest to all. Unfortunate- turn, these studies were organized into four categories
ly, representatives of both sides of the abortion debate according to research design: case studies (17), con
often exercise a high degree of selectivity in their trolled studies (14), retrospective-uncontrolled studies
review of the psychological sequelae literature, publi- (20) and prospective-uncontrolled studies (23). Each of
cizing only findings that support their position on the these four types of research designs have strengths and
matter. This is unfortunate because when thoughtfully weaknesses, some of which will be described below.
approached, it becomes evident that the question of
possible sequelae to abortion exists apart from the ethics Unfortunately, there are many inconsistencies in the
of the action. This is true for two reasons. First, doing conclusions drawn by the authors of the studies we
what is "right" or "wrong" may or may not result in located. For example, Wallerstein, Kurtz and Bar-Din
changes in the emotional state. For example, evangeli- (1972) found adverse reactions in fifty percent of the
cal Christians base the correctness of an action on their cases studied, while Osofsky and Osofsky (1972), in a
interpretation of the Scripture. Relative to a directive study published the same year, concluded that there
or principle found in Scripture, an emotional reaction were few, if any, adverse psychological reactions.
or the absence of the same in women who have had When results are this varied, both pro-life and pro
abortions is of little consequence in providing moral choice camps are able to find "evidence" to support
guidance. Second, one key issue in determining the their position. Under such circumstances, the need to
morality of abortion is the question of the "rights of the consider the methodological and statistical practices
unborn." A woman's psychological reaction to abortion underpinning each study becomes self-evident. A
offers little direction concerning whether or not these review of the foundations on which the literature rests
rights have been violated. sometimes can differentiate between studies that can
be trusted and those that come to unwarranted conclu
In this paper we do not wish to address questions sions. If severe methodological flaws in the current
surrounding the morality of abortion. Rather, we want literature do exist, these inadequacies, not the conclu
to provide a review of the psychological sequelae sions reached, should be the focus of attention. Thus, it
literature aimed at determining the scientific merit of is the experimental validity rather than the conclusions
existing studies. Certainly it would be reprehensible to of existing studies that provide the focus of this paper.
overstate or understate a scientifically validated find
ing for a "higher" moral cause. Likewise, it would be
reprehensible to pass on as "scientific" the claims of Conceptualizing Validity
studies that exhibit little experimental validity. We elected to adopt a conceptualization of experi
mental validity proposed by Cook and Campbell (1979)
To determine the level of rigor that exists in the to help systematically determine how seriously the
psychological sequelae literature, we have undertaken conclusions of a given study should be taken. Experi
a review of this literature from a methodological and mental validity can be categorized into four different
statistical perspective. To locate articles we have relied types: statistical conclusion validity, internal validity,
upon computer searches of Index Medicus, Psychologi- construct validity and external validity. Statistical con
cal Abstracts, Science Citation Index and the National clusion validity is concerned with the extent to which a
Institute of Mental Health data base in addition to study permits valid inference about covariation
examination of the bibliographies of all articles located. between the independent variable (the presence or
This search yielded over 300 studies; seventy-six were absence of abortion) and the dependent variable (some

J. L. ROGERS, J. F. PHIFER AND J. A. NELSON

W *Nam

PSYCHOLOGICAL EFFECTS OF ABORTION

Table I

Statistical Power for Fourteen Comparative Studies That Examine the Psychological Sequelae of Abortion

Sample Sizc _ Harmonic Relative Date

Researcher N n~ nb Wan Power Coun try (Data Collected)

98,612 71,378 39,426 .99+ 1974-75

7,660 4,110 3,809 .99+ 1975-76

30,329 28,556 3,338 .99+ 1952-56

ill 18 30 .12 1963-69

42 21 21 .10 1960-68

128 47 59 .17 1971-72

126 63 63 .17 1972-73

68 19 27 .12 1971-72

114 38 51 .16 1970-72

300 108 138 .27 1967-68

157 69 77 .19 1974-75

152 58 72 .19 1968-70

78 46 38 .13 1955--63

102 22 35 .13 1968-70

Notes: For the purpose of power estimation, we have assumed the following: 1) that "ideal" experimental arrangements exist throughout the literature; namely, that all existing studies perfectly measure an identical outcome parameter that reflects level of depression and that perfect subject equivalency exists at baseline across the two conditions; 2) that post-event depression will be five percent greater in women experiencing abortion than women who carry to term, i.e., that there will be 25% postabortion depression vs. the 20% postpartum depression rate reported by Hopkins, et al., (1984), and 3) that a one tailed z test with alpha set at .05 on transformed proportions is used as the test statistic.

Power values were determined as outlined by Cohen (1977). In accordance with Cohen's guidelines for unequal sample sizes, the abortion and control group sample sizes (n. and nb, respectively) were converted to a single harmonic mean which was used to enter the power tables.

L. ROGERS, J. F. PHIFER AND J. A. NELSON

PSYCHOLOGICAL EFFECTS OF ABORTION

J. L. ROGERS, J. F. PHIFER AND J. A. NELSON

J. L. ROGERS, J. F. PHIFER AND J. A. NELSON

PSYCHOLOGICAL EFFECTS OF ABORTION

REFERENCES

L. ROGERS, J. F. PHIFER AND J. A. NELSON