Genetics

Studies

Bailey & Pillard (1990) Terms to define

• Genes

• Kinship Studies

• Inheritance

Bailey & Pillard (1990) Aim

To investigate a possible genetic basis of sexual orientation

Bailey & Pillard (1990) Procedure

• Monozygotic (MZ) and dizygotic (DZ) twins, as well as adoptive brothers, were recruited through gay publications.

• All participants were voluntary, male, and twins were raised together in similar environments.

• Sexual orientation of relatives was assessed by asking relatives directly or relying on the gay participant’s report.

• Childhood Gender Non-conformity (CGN) was assessed using questionnaires.

• CGN refers to children not conforming to expected gender behaviors or identifying with the opposite gender.

• Examples of CGN include cross-gender clothing preferences, playing with opposite-gender-associated toys, preferring opposite-gender playmates, and identifying with opposite-gender characters in media

Bailey & Pillard (1990) Results

• 52% of MZ twins identified as homosexuals

• 22% of DZ identified as homosexuals

• 11% of the adoptive brothers identified as homosexuals

• A more closely genetically linked par is more likely they are to show gay or straight tendencies

• They self-reported history of childhood gender non-conformity did not predict homosexuality

• Finally childhood gender nonconformity does not appear to be correlated with the development of homosexuality

Bailey & Pillard (1990) Evaluation

Weissman (2005) Terms to define

• Genes

• Longitudinal study

• Major depressive disorder

Weissman (2005) Aim

To study the potential genetic nature of major depresive disorder

Weissman (2005) Procedure

• The study had a span of 20 years, examining families at high and low risk for depression.

• The original sample of depressed patients (grandparents) was selected from an outpatient clinic specializing in mood disorders. As well as the non-depressed participants

• Parents and children from the original sample were interviewed four times over this period.

• The children, now adults with children of their own, gave the study a third generation.

• Data was collected by clinicians, blind to past depression diagnoses or prior interview data.

• Researcher triangulation was used to establish credibility.

• Children were evaluated by a child psychiatrist and a psychologist.

Weissman (2005) Results

• High levels of psychiatric disorders in the grandchildren with two generations of major depression

• By 12 years old, more than 50%og the grandchildren showed signs of psychiatric disorders (commonly anxiety)

• Children of prior generations of depression had a higher risk of having any disorder

• The severity of a parent’s depression was correlated with an increased rate of mood disorders in the children

Weissman (2005) Evaluation

Genetics and studies general behavior

• No behavior is the result of a single gene

• Genetics is a reductionist approach to behavior

• Problems with construct validity (e.x. how depression was operationalized for a study

• These kinds of studies only study genetics inderectly