Childhood social adversity increases schizophrenia risk

Social adversity in childhood appears to be independently associated with the risk of developing schizophrenia and other psychoses later in life, report researchers in findings that suggest the risk increases with greater levels of exposure to adversity.

"There is conflicting evidence concerning the association of social childhood factors and subsequent psychosis," note Susanne Wicks (Stockholm Centre for Public Health, Sweden) and colleagues.

To investigate whether there is indeed a relationship, the team studied data for all children born in Sweden between 1963 and 1983 into family households that participated in a national census in 1970, 1980, 1985, or 1990. In total, 2.1 million children were included.

The risk of being hospitalized for schizophrenia or other psychoses between 1987 and 2002 was then estimated for five different indicators of socioeconomic position - living in rented apartments, low socioeconomic status, single-parent households, unemployment, and households receiving social welfare benefits.

The team found that most of the social factors were independently associated with an increased risk of schizophrenia and other psychoses, with hazard ratios ranging from 1.6 to 2.4. The greatest risk was linked to receipt of social welfare benefits, with living in a rented apartment associated with the lowest risk. The hazard ratios for other psychoses and social risk varied between 1.5 and 2.5.

Moreover, the results showed that the risk of developing schizophrenia or other psychoses increased as the number of adverse social factors increased. Individuals exposed to four or more measures of adversity were 2.7 times more likely to develop schizophrenia than those exposed to no adverse conditions.

Reporting in the American Journal of Psychiatry, Wicks et al. suggest that social adversity and exclusion could lead to isolation, alienation, and a stressful life situation, which, in turn, provides fewer opportunities for social support. In genetically vulnerable individuals, these situations could be of significance in developing schizophrenia or other psychoses, they say.

The researchers conclude that if the relationship between psychosis and social factors are assumed to be causal, "about 20% of the cases of schizophrenia and 19% of the cases of other psychoses could be attributed to adverse social exposure."

They add: "Social factors maybe significant factors to be considered."

Am J Psychiatry 2005; 162: 1652-1657