Key early studies: Zurich Cohort Study

In the Zurich Cohort Study, a group of adults aged 20‒30 years was selected, with two-thirds being high scorers on the Symptom Checklist 90-R.¹ In individuals with pure depression, pure anxiety, or comorbid depression and anxiety, childhood conflicts between parents, conflicts with parents, sexual trauma, lack of attention, low prestige of family, and more severe punishment were all significantly more common than in control subjects.¹

References:
1. Angst J, Vollrath M. The natural history of anxiety disorders. Acta Psychiatr Scand 1991; 84 (5): 446–452.

2. Merikangas KR, Zhang H, Avenevoli S, et al. Longitudinal trajectories of depression and anxiety in a prospective community study: the Zurich Cohort Study. Arch Gen Psychiatry 2003; 60 (10): 993–1000.