What does research say about the relationship between lithium and memory?

Lithium slows cognitive decline in people with mild memory complaints and early Alzheimer's disease. A meta-analysis of three randomised trials (232 participants) showed a significant effect in favour of lithium over placebo. In one of those trials, involving 45 people with mild cognitive decline, a biological marker of brain cell damage (phospho-tau) in the cerebrospinal fluid also fell after twelve months, while memory and attention scores improved. A separate small study in Alzheimer's patients found that an extremely low dose (300 micrograms per day, far below the usual psychiatric dose) stabilised decline on a cognitive test three months earlier than expected. That last study was small, so the results deserve cautious interpretation.

For people who already use lithium for a bipolar or unipolar disorder, the picture looks different. Several studies, including a double-blind cross-over experiment in 16 patients, found no measurable memory loss from lithium. What lithium does do is slow psychomotor speed, so you react and move slightly more slowly. Subjective memory complaints reported by patients are in practice more often associated with residual depressive symptoms than with lithium itself. The literature on this specific use is contradictory, partly because studies differ considerably in design and patient populations.

Animal research provides clues about a mechanism: in mice with an Alzheimer-like disease model, a low dose of lithium prevented memory decline, reduced the formation of harmful plaques in the brain, and increased a protein that supports brain cell growth. Findings in mice do not automatically apply to humans, but they point the way for further research.

Whether lithium also helps healthy people remember better has not been demonstrated. A review study concludes that cognitive benefits only appear to become visible when the nervous system is already under pressure, for example due to illness or stress. People who use lithium because of thyroid or kidney problems face a greater risk of side effects with long-term use; these should be monitored.