Primarily neutral effects were found in 14 of the 34 studies reviewed here. 

Rasmussen (1934) 

This Norwegian study of 54 sexual assault cases involving children from 9-13 years of age, which were selected from court records, focused on adult mental health and social adjustment. Victims had been medically examined and the offender convicted. There was no control group with this offender population. As mentioned previously, we do not know exactly what the evidence was that led to Rasmussen's conclusion that 85% seemed none the worse for the experience. However, this early study provided much needed information on an offender population which has been used to compare results from other descriptive studies and shows a trend. It does not present  conclusive evidence. 

Bender and Grugett (1952) 

Social and psychiatric follow-up information was collected on 14 adults who as children, 11 and 16 years previously, had been referred for psychiatric attention by a children's court because of various and prolonged sexual experiences. The authors' conclusion that there exists no scientific proof that there are any resulting deleterious effects must be tempered by the knowledge that the small population studied was clinical and there was no control group.

Landis (1956)

Of the 1,800 university students from middle- to upper-class backgrounds who completed questionnaires for this study, 500 were found to have had childhood experiences with adults. The authors' conclusion that "the great majority of the victims seemed to have few permanently harmful effects from the experiences" (p. 108) can be accepted based on the clear definition of terms, large number of 

cases studied, use of a large control group, a non-clinical & non-offender population, and acceptable measures of consequences. He did combine age groups (4-19 plus years), however, and his findings could not be generalized to lower-class populations. 

Brunold (1964) 

The information for Brunold's Netherlands study of 62 sexual assault cases from court records was gathered by personal and third person interviews at least 15 years after the offense. There was no control group, and an offender population was used. 
His conclusion that lasting "psychological" injury as a result of sexual assaults suffered in infancy is not very common can be questioned in several years. [?ways?]
First, he admittedly did not consider personality in his measures of consequences but based his conclusions on background, education, later occupation, and marital relationships, not psychological aspects. 
Second, his use of the term "infancy" is dubious since all his cases were from 5 to 15 years of age at the time of the offense. *

* The inappropriate use of terms could be due to inaccurate translation from the original language.

Gagnon (1956) 

Gagnon studied the 333 women who reported a sexual experience with an adult before age 13 in the Kinsey study by structured interviews. His use of a control group, large number of cases, clear definition of terms, and specific measures of consequences make his finding that "only 5% could be considered to have adult lives that had been severely damaged for whatever reason" (p. 188) acceptable. It must be remembered, however, that his population was primarily college-educated women, and it is a retrospective study.

Lukianowicz (1972) 

This was an Irish study of 55 incest cases with lower-class backgrounds found in a general hospital. Information was obtained by psychotherapy interviews. No control group was used. The finding that "the incestuous activities seemed to have been only a transitory, culturally permissable phase in the process of their normal Psychosexual development, and as such did not result in any bad effects" (p. 312) may need to be limited to this particular culture and to a lower-class, clinical population. 

Herman and Hirschman (1977) 

These authors studied 15 "father-daughter" incest cases where the victims were later seen in psychotherapy. Their use of the term "father-daughter" is misleading because three stepfathers, a grandfather, a brother-in-law, and an uncle were included. Herman and Hirschman observed that "nothing  

obvious distinguished them from the general population of women entering psychotherapy" and that "the severity of their complaints seemed to be related to the degree of family disorganization and deprivation in their histories rather than to the incest history per se" (p. 745). The familiar sampling trilogy of a few cases, no control groups, and a clinical population, plus the loose definition of terms and descriptive measures of consequences, make these findings questionable. They can only discern a trend.

Goodwin, Simms, and Bergman (1979) 

In a study similar to that of Gross (1979), Goodwin et al. describe six cases in which adolescents developed hysterical seizures after parental incest. A difference is that Gross' subjects experienced incest as adolescents whereas Goodwin et al.'s subjects experienced incest below the age of 10, and the seizures disappeared after psychotherapeutic exploration of the incestuous experience. This descriptive study raises questions for further investigation.

Symonds, Mendoza, and Harrell (1981) 

The 109 cases of incest were self-identified in response to advertisements in newspapers and studied by phone interviews. Respondents were middle-class and, overwhelmingly, white males. This sampling bias, plus no control group and only descriptive measures of consequences, make the author's conclusions applicable only to white, middle-class self-selected males in Los Angeles. A more sophisticated analysis of data would have been helpful.

Nelson (1981) 

The findings of this exploratory, descriptive study on incest were based on survey data from 100 persons who responded to classified advertisements in periodicals. The majority were middleclass, male, and from San Francisco and the Bay area. A high proportion were homosexuals, and ages at time of incest ranged from 3-up years. The lack of a control group, a biased, self-selected sample, the combination of children and adult experiences, and the large number of homosexual males cause the findings to be questionable, although trends may be discerned. 

Finkelhor (1981) 

Finkelhor used questionnaires to study 796 college students, 114 of which had sibling sexual experiences, in a predominantly white, middle-class sample. He used comparison groups and separated the sample by ages at time of the experience for purposes of analysis. He included "an invitation to do something sexual" as a sexual experience and also included step-sibling and half-siblings, which could skew his findings somewhat. He did not, however, use the value-laden term of "victimization" in relation to sibling sex as he does in 

relation to other older partners. Although he had three limited indicators of adult sexual behavior, his study was, admittedly, not well equipped to grapple with outcomes. He did move beyond the typical descriptive conclusions regarding outcome to statistical analyses, however. His finding that there is little reason to think that sibling sexual experiences are influential for adult sexual functioning should be considered as evidence. 

Fritz, Stoll and Wagner (1981) 

This study of 952 college students through questionnaires used comparison groups, well-defined terms, and separated the sexes for purposes of analysis of prepubescent sex play. A strength of this study was that some parametric statistical measures were used for measures of consequences. A limitation was that only adult sexual adjustment was studied. Fritz et al. found that 1,8% of all females have problems with adult sexual adjustment arising from prepubertal molestation and that molested males and females differ significantly in regard to long-term effects on sexual attitudes and relationships. This study did meet our scientific criteria, and the findings should be considered.

Emslie and Rosenfeld (1983) 

These authors compared 7 incest cases with a control group of 19 cases, all of whom were hospitalized for psychiatric problems. Definitions were clear, and the use of a control group made possible the comparison of effects. No difference was reported. However, the small number of cases, use of a clinical population, the combining of age groups, and no specificity of socio-economic class were given. No generalizations could be made from the finding.

Kilpatrick (1986) 

Kilpatrick used a deliberate sample in order to increase heterogeneity in her study of the childhood (0-14 years) sexual experiences of 501 predominantly middle-class women. Women with childhood sexual experiences were compared with those who had no such experiences. Her terms were well defined. A primary strength of this study was that the researcher utilized quite sophisticated analytic procedures, such as hierarchical multiple regression analyses, in order to determine long-term effects on five different measures of present adult functioning. With this type of procedure, factors such as background variables could be controlled. 
Her findings were that adult functioning of women who had childhood sexual experiences and those who had none did not differ significantly. However, sexual experiences that were abusive, forced, guilt-producing, harmful, or pressured interacting with the type partner (parents, other relative, non-relative) were significant for all measures of adult functioning except for the sexual satisfaction scale. Her findings should be considered.