Population based register studies

We have shown that

1. the longitudinal course of illness in depressive disorder and in bipolar disorder on average is progressive in nature with increasing severity of depressive episodes, increasing risk of recurrence of depressive and manic episodes
2. the prevalence of cognitive dysfunction may increase for every new affective episode
3. the risk of developing dementia is increased in unipolar and bipolar disorders compared to the general population
4. the risk of developing dementia seems to increase with progression of the disorders
5. continued treatment with lithium seems to decrease the risk of developing dementia to the level of the general population.