Weissman et al

Kinship Study on MDD

Aim

To examine the heritability of major depressive disorder (MDD) across three generations.

Sample

Weissman et al (2005) carried out a longitudinal family study with a sample of 161 grandchildren and their parents and grandparents to study the potential genetic nature of Major Depressive Disorder.

Procedure

·      The study took place over a twenty year period, looking at families at high and low risk for depression. The original sample of depressed patients (now, the grandparents) was selected from an outpatient clinic with a specialization in the treatment of mood disorders. 

·      The non-depressed participants were selected from the same local community.

·      The original sample of parents and children were interviewed four times during this period.  The children are now adults and have children of their own - allowing for study of the third generation.

·      Data was collected from clinicians, blind to past diagnosis of depression or to data collected in previous  interviews. In order to establish credibility, researcher triangulation was used.  Children were evaluated by two experienced clinicians - with one being a child psychiatrist and the other a psychologist.

Results

·      The researchers found high rates of psychiatric disorders in the grandchildren with two generations of major depression. By 12-years-old, 59.2% of the grandchildren were already showing signs of a psychiatric disorder - most commonly anxiety disorders. 

·      Children had an increased risk of any disorder if depression was observed in both the grandparents and the parents, compared to children where their parents were not depressed.

·      In addition, the severity of a parent's depression was correlated with an increased rate of a mood disorder in the children.

·      On the other hand, if a parent was depressed but there was no history of depression in the grandparents, there was no significant effect of parental depression on the grandchildren.