Dear Dr. Aiken: You recommended lithium for suicidal patients in the TCPR 2018 summer issue, but isn’t there a risk of overdose with this strategy?

Dr. Aiken: From firearms to bridges, the suicide rate goes down when we erect barriers to the means. Barriers work because suicidal impulses are brief, lasting only 1–2 hours on average. It would seem intuitive, then, that withholding lithium, which is toxic in overdose, from a suicidal patient is a safe move. However, intuition doesn’t match up with the evidence here.

Lithium stands in stark contrast to most other psychiatric medications, which carry a widely debated black box warning about increased suicidality. There is no evidence that lithium raises the suicide risk, and there is strong evidence that it does the opposite. People with mood disorders carry a risk of suicide that’s 10–20 times higher than the general population, but when they take lithium, that risk falls to a level that is indistinguishable from the norm. This is true for completed and attempted suicide, in both unipolar and bipolar disorders, and is based on data encompassing over 110,000 person years (Tondo L et al, Curr Psychiatry Rep 2016;18(9):88).

That’s impressive, but it’s just observational data, and it could hide a bias. Perhaps doctors steer away from lithium in suicidal patients, which would explain the low suicide rates in patients treated with lithium. Randomized controlled trials (RCTs) suggest otherwise. In a meta-analysis of RCTs involving 2,400 patients, lithium reduced the risk of completed suicide by 60% compared to placebo (Smith KA et al, Bipolar Disord 2017;19(7):575–586). Those results were quickly followed by a case-controlled study of 50,000 patients, which confirmed that this protective effect was unique to lithium and not seen with other mood stabilizers (Song J et al, Am J Psychiatry 2017;174(8):795–802).

Though it’s a counterintuitive leap to prescribe lithium to a patient with a history of overdose attempts, it may be the only medication that can prevent those attempts. Lithium doesn’t seriously change access to suicidal means given that a lethal dose of Tylenol—about 50 pills—is available in most medicine cabinets. That’s why I prescribe lithium to suicidal patients, even if they’ve overdosed in the past. As a precaution, I tell them that lithium is rarely fatal in overdose, although often disabling. If a patient’s risk is acute, I engage the family to dispense the medicine one night at a time.

On the other hand, I’ve had a number of patients overdose on benzos, and in those cases I don’t give a second chance. True, anxiety is a risk factor for suicide, so intuitively one would expect benzodiazepines to lower this risk. Suicide, however, is not rational, and once again the data fly in the face of intuition. Both controlled and naturalistic studies suggest that benzodiazepines don’t lower the suicide risk and may actually raise it (Dodds TJ, Prim Care Companion CNS Disord 2017;19(2). doi:10.4088/PCC.16r02037).

Though they shake my intuition, these findings also remind me that the highest aim for psychotropics is to improve functioning, not feelings. Lithium, with its anti-impulsive effects, comes close to that goal. Patients may feel better with benzos, but their functioning rarely improves, and the disinhibition these agents cause can do the opposite, at least when it comes to suicide.