Is polarity of recurrence related to serum lithium level in patients with bipolar disorder

Recently published data might indicate that the polarity of recurrence is related to lithium serum levels. To systematically test this hypothesis all published maintenance trials in bipolar disorders were examined with regard to this issue. Maintenance studies were subdivided in trials with low (i. e. below 0.6 mEq/l),medium (i. e. 0.6 to 0.8 mEq/l) and high (i. e. above 0.8 mEq/l) lithium serum levels. Percentage of depressive vs. (hypo-)manic or mixed recurrences were compared for these three groups. The percentage of depressive recurrences in the groups with low, medium and high lithium levels differed in a clinically and statistically significant manner (12% vs. 38% vs. 64%, p<0.0001). The results might indicate that low lithium levels are effective in preventing depression whereas higher blood levels are needed to prevent (hypo-)manic or mixed states.