Onset-age of bipolar disorders at six international sites

Abstract Background Onset-age is a stable characteristic of bipolar disorder (BPD) patients of clinical and probable psychobiological importance, but large pooled clinical samples from multiple sites employing modern diagnostic criteria to quantify onset-age remain rare. Methods We pooled diagnostic, demographic, and clinical data from 1566 BPD patients from six international sites (5 European, 1 US) to compare onset-ages in subgroups. Results Median ± IQR onset in 1090 BP-I patients was 5.8 years younger than 476 BP-II cases (24.3 ± 18.3 vs. 30.1 ± 13.8 years; p < 0.0001). Onset-age ranked: [a] BP-I men (23.0 ± 12.8); [b] BP-I women (26.0 ± 14.2); [c] BP-II men (29.7 ± 19.1); and [d] BP-II women (30.1 ± 17.5 years. Juvenile-onset (≤ age 20) was more common in Europe than the US (27% vs. 16%), as was childhood-onset (< 13 years: 3.3% vs. 0%; both p < 0.001). Proportion of all cases, and median onset for first episodes ranked: [a] BP-I psychotic (6.3%; 22.7 ± 9.2); [b] BP-I manic (29.3%; 24.0 ± 12.1); [c] BP-I depressed (25.1%; 24.5 ± 14.9); [d] BP-I mixed (9.7%; 27.9 ± 16.0); [e] BP-II depressed (26.9%; 30.0 ± 19.5); and [f] BP-II hypomanic (2.8%; 33.6 ± 15.1 years; p < 0.0001). Among BP-I patients, onset was similar for various forms of mania and major depression; in BP-II patients initial depression was 9.6-times more frequent and diagnosed earlier than hypomania. Limitations There was some variance among sites and only 34.1% of patients were evaluated at onset. Conclusions Type I BPD began much earlier than type II; its mainly psychotic presentations occurred earliest, but BP-I men were younger than women, especially at psychotic or mixed onsets.