Does lithium prevent suicide? A large trial complicates an old belief

The long-held belief that lithium specifically guards against suicide rests mostly on observational data and older trial meta-analyses; when the question was tested directly in a randomised trial, adding lithium to usual care did not reduce suicide-related events [s1][s2]. That trial, in 519 US veterans with depression or bipolar disorder who had recently survived a suicide-related event, was stopped early for futility [s1].

Suicide is a persistent and rising public-health problem, and lithium — a mood stabiliser used for decades in bipolar disorder — has long carried a reputation for doing something no other psychiatric drug reliably does: lowering suicide risk in its own right [s1]. The evidence for that reputation and a trial built to confirm it now point in different directions, and the gap between them is instructive.

What the older evidence showed

The case for lithium was anchored by a 2013 systematic review and meta-analysis pooling 48 randomised trials and 6,674 participants [s2]. Compared with placebo, lithium was associated with fewer suicides (odds ratio 0.13; 95% CI, 0.03 to 0.66) and fewer deaths from any cause (odds ratio 0.38; 95% CI, 0.15 to 0.95) [s2]. In unipolar depression specifically, it was linked to a reduced risk of suicide (odds ratio 0.36; 95% CI, 0.13 to 0.98) [s2]. The signal was not uniform: lithium showed no clear benefit over placebo for deliberate self-harm (odds ratio 0.60; 95% CI, 0.27 to 1.32) [s2].

Those are striking numbers, but suicide is a rare event even in high-risk groups, so the estimates rest on small event counts and carry the wide confidence intervals to prove it [s2]. Pooled trials also enrolled patients for maintenance treatment of mood disorders, not people selected because they had just survived a suicidal crisis.

What the trial found

That harder test was the point of a US Department of Veterans Affairs cooperative study — a double-blind, placebo-controlled trial across 29 VA medical centres [s1]. It enrolled veterans with bipolar disorder or depression who had had an episode of suicidal behaviour, or an admission to prevent suicide, within the previous six months, and randomly assigned them to extended-release lithium carbonate (starting at 600 mg a day) or placebo added to their usual care [s1]. The outcome was time to the first repeat suicide-related event [s1].

The trial was stopped for futility after 519 veterans were randomised — 255 to lithium and 264 to placebo [s1]. There was no overall difference between the groups (hazard ratio 1.10; 95% CI, 0.77 to 1.55) [s1]. In all, 127 participants (24.5%) had a suicide-related outcome: 65 in the lithium group and 62 in the placebo group [s1]. Mean lithium blood concentrations at three months were modest — 0.54 mEq/L in patients with bipolar disorder and 0.46 mEq/L in those with major depressive disorder [s1]. No unanticipated safety concerns emerged [s1].

Reconciling the two

The trial's authors drew a careful conclusion: simply adding lithium to existing regimens is unlikely to prevent a broad range of suicide-related events in patients already being actively treated for mood disorders and substantial coexisting illness [s1]. That is not the same as saying lithium never helps. This population was high-risk and heavily comorbid; the drug was an add-on to complex real-world care rather than the centrepiece of a clean maintenance regimen; and blood levels were on the low side [s1]. What the trial undercuts is the specific hope that layering lithium onto existing treatment, chiefly to reduce suicide risk, will work in this hard-to-treat group — not lithium's established value as a mood stabiliser [s1].

For related evidence on interventions studied for acute suicidal states, see our coverage of a meta-analysis of ketamine for suicidal and depressive symptoms, and of serial ketamine for treatment-resistant bipolar depression.

What it means

Lithium remains a mainstay for bipolar disorder and an established option in treatment-resistant depression [s1][s2]. But the strongest direct test to date does not support adding it to usual care purely as a suicide-prevention measure in already-treated, high-risk patients — a reminder that an effect seen in pooled older trials can shrink to nothing when tested head-on in the group it was meant to help [s1][s2].

What to watch

Whether targeting by diagnosis, achieved blood level or specific populations changes the result, and whether future trials separate lithium's mood-stabilising role from any distinct effect on suicide risk.

This article describes trial evidence and is not medical advice. Anyone struggling with thoughts of suicide should seek help from a clinician or a local crisis service.

Sources

1. Lithium Treatment in the Prevention of Repeat Suicide-Related Outcomes in Veterans With Major Depression or Bipolar Disorder: A Randomized Clinical Trial — JAMA Psychiatry, 17 November 2021
2. Lithium in the prevention of suicide in mood disorders: updated systematic review and meta-analysis — BMJ, 27 June 2013