Objective: The genetic phenomenon of anticipation is a pattern of inheritance that includes earlier age at onset and increased severity of symptoms in succeeding generations, and is a feature of some neurodegenerative diseases. This phenomenon is suggested to occur in bipolar disorder (BP) as well.
Method: Anticipation in children with BP type 1 (s2) (n = 31) and their parents (s1) (n = 31) not-consecutive generations-was assessed by analyzing clinical characteristics and prognoses.
Results: Age at onset of BP type 1 in s2 (mean: 19.3 +/- 4.2 years) occurred earlier than in s1 (mean: 29.5 +/- 10.2 years) (u = 345, P < 0.001). There was a direct negative correlation between the s1 and s2 cases (r = -0.554, P < 0.001). The total number of episodes in s1 (13.9 +/- 12.3) was greater than in s2 (8.7 +/- 7), which had a higher frequency of episodes (0.6 +/- 0.3 and 1.5 +/- 1.2) (u = 357, P < 0.001). There was a direct correlation between total episodes and the frequency of manic episodes between s1 and s2 (r = 0.312, P < 0.001 and r = 0.365, P < 0.001, respectively). We observed that 72.7% of BP type 1 parents that had episodes with psychotic features had offspring that had episodes with psychotic features.
Conclusions: Results of this study show that age at onset was earlier and the frequency of episodes was greater in s2 BP type 1 cases. In addition, episodes with psychotic features might be a marker for genetic anticipation.