Genetic liability, illicit drug use, life stress and psychotic symptoms: preliminary findings from the Edinburgh study of people at high risk for schizophrenia

Background: Studies of groups at high risk of developing schizophrenia have tended to be based on subjects recruited to the study in their infancy. This paper reports on subjects at genetic high risk for schizophrenia assessed as young adults, close to the age when most onsets of schizophrenia occur. Methods: One hundred and fifty-five young people at elevated risk for the development of schizophrenia and 36 controls not at increased risk were assessed on entry to the Edinburgh High Risk Study. The measures included current psychotic symptoms, past and present cannabis and other drug use, lifetime life events and two aspects of genetic liability to schizophrenia. Results: Cannabis and other illicit drug use were significantly associated with symptoms in both groups. The same held true for the more upsetting life events experienced, but not for less upsetting ones. Within the high-risk group, there was no relationship between symptoms and a measure of genetic loading, but there was some slight evidence of a higher risk of symptoms when affected relatives were on the father's rather than the mother's side of the family. Conclusions: Cannabis use, use of other illicit substances and upsetting life events may all lead to psychotic symptoms in vulnerable young people.