When Lady Gaga recently spoke in an interview about taking lithium while suffering from a “psychotic break”, it drew attention to a drug that has long been used in psychiatry but is less widely understood outside it.

Lithium has been used in psychiatric care for more than 70 years, most notably to treat bipolar disorder. Alongside this renewed attention, a recent study has explored whether much lower doses of lithium might help protect the ageing brain – raising questions about whether its effects could extend beyond mental health treatment.

But the science tells a more complicated – and more sobering – story.

Lithium is a naturally occurring chemical element, found in soil, rocks and water. Most people consume tiny amounts of it through drinking water and foods such as vegetables and grains.

In medicine, it is prescribed in the form of lithium carbonate or lithium citrate. At the doses used in treatment, it steadies mood by reducing how often and how severely manic and depressive episodes occur.

It is also one of the few psychiatric medicines shown to reduce the risk of suicide. In the UK, lithium is licensed for bipolar disorder, mania, severe depression and some forms of aggressive or self-harming behaviour.

Despite decades of use, scientists still do not fully understand how lithium works. What is clear is that it acts across multiple systems in the body at once – affecting brain chemicals such as serotonin and dopamine, helping the immune system function more evenly, and........

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