Background. Many social and demographic correlates of psychiatric disorder have shown marked secular changes in recent decades. This study was designed to explore some of the implications of these trends, focusing on the illustrative case of teenage motherhood.

Method. Prospective data from two British birth cohort studies (the 1946 and 1958 cohorts) were used to examine the social, educational and behavioural precursors of teenage versus older age at motherhood, and the implications of teenage motherhood for women's later marital and social circumstances and risks of psychiatric morbidity, in samples born 12 years apart.

Results. Educational and social disadvantage were associated with similarly increased risks of teenage motherhood in both cohorts, but the findings suggested an additional association with teacher-rated adolescent conduct problems in the more recent sample. Rates of teacher-rated emotional problems were not elevated among teenage mothers in either cohort. In adult life, teenage motherhood was associated with a range of adverse social outcomes, including partnership breakdowns, large family size, and poorer housing conditions. Relative risks of these adult adversities were similar for teenage mothers in the two cohorts, but absolute levels of adversity were higher in the more recent sample, reflecting general secular changes in many of the indicators involved. In the later, but not the earlier, cohort, teenage motherhood was also associated with increased risks for psychiatric morbidity in adulthood.

Conclusions. The findings underline the importance of taking account of secular trends in examining the impact of psychosocial risks.