Hair disorders are another set of conditions that are frequently associated with psychotropic medications, including lithium. There is a known strong association between alopecia and sodium valproate. As with skin disorders, the evidence is very limited, mostly comprising case reports. Electronic searching (by the author RM, January 2014) found a total of 25 publications reporting an adverse effect on lithium upon hair, 15 of which were case reports. These are summarised in Table 15.2. Many of the patients described in these reports were taking several psychotropic medications: confounders may therefore be clouding the picture.

One RCT comparing lithium (n = 91) to placebo (n = 94) for 12 months reported hair loss in 8 % of patients in the lithium group compared with 6 % in the placebo group; this was a non-significant difference (Bowden et al. 2000). Similarly, another RCT also reported no significant difference in hair loss between lithium-treated patients (3 %) and placebo (0 %) (Calabrese et al. 2005). Several cross-sectional studies on groups of patients taking lithium reported ‘hair thinning’ during the 1970s and 1980s (see summary in McKnight et al. (2012)). However, in all these cases, the patients self-reported a problem with their hair—often spontaneously—and there were no diagnostic criteria or guidance as to what and how it should be recorded. To reliably characterise the association between lithium and skin/hair disorders, further evidence is needed. Trials should gather routine data as part of adverse events reporting.

It is clear from the above that, whilst lithium is an effective drug, it brings with it a high risk of dose-related adverse effects. To ensure continued safe prescribing, it is recommended that patients should have baseline tests before commencing therapy and at regular intervals thereafter. Based on the evidence outlined above (and the recent UK clinical guidance (NICE 2014)), Table 15.3 outlines recommendations for clinical monitoring.

Lithium is a classic exemplar of a psychotropic drug: it is highly efficacious at stabilising mood in both unipolar and bipolar mood disorders but has a multitude of short- and long-term side effects. There is good evidence for its association with thyroid disorders, hyperparathyroidism, weight gain and various short-term conditions. Further evidence is needed to fully understand the risk factors and epidemiology of these adverse effects and to substantiate claims of a link with hair and skin disorders.

Given that lithium is an established effective treatment, future clinical trials are likely to compare it to newer therapeutics, probably over a relatively short time period of several months. Routine baseline and follow-up data on endocrine, metabolic, skin and hair parameters would provide high-quality data and fill the current knowledge gaps, whilst biobanks and other databases may add other physiological and genetic data to clinical observations. Large prospective cohorts—perhaps those set up for other purposes, e.g., new mood-monitoring technology—could help to refine our epidemiological knowledge of this aspect of lithium’s side effects (Bopp et al. 2010).

Managing patients on lithium will always be a matter of balancing risks; improving our knowledge of the adverse effects of lithium will allow clinicians to provide the highest quality of care for mood disorders safely and effectively. Elucidating its mechanism of action and developing less toxic analogues should remain a priority.