This paper illustrates the use of cohort data from a population to describe the early life prevalence and odds ratios (ORs) of the main classes of International Classification of Diseases (ICD) associated with any mental disorder arising at any time during the 16 year study period.

The main ICD disorder classes were examined in relation to psychiatric disorders over 16 years in a cohort under the age of two years between April 1st, 1993, and January 1st, 1995.

To demonstrate the utility of studying the complete profile of associated diagnoses over time in a population cohort.

The total number of individuals under the age of two years before 1995 (n = 17,603) were tallied within each main class of ICD disorder by year and expressed as ORs of those with and without any 16-year psychiatric disorder.

The greatest annual rates observed in the early years of life were for the following main ICD classes of disease: respiratory system, sense organs, symptoms signs ill-defined conditions, no diagnosis, injury poisoning, and skin subcutaneous tissue disorders. These disorders also had the highest ORs in early life given the presence of a mental disorder at any time during the study period.

Knowing the early life main class diagnoses associated with psychiatric disorders could guide both basic science research as well as early intervention social and health investment policies.

The authors have not supplied their declaration of competing interest.