A series of studies providing the best data on the long term effects of lithium has been coming out of a large database of healthcare use and diagnoses called the Danish Psychiatric Central Research Register.
Because healthcare is nationalized in Denmark, this register covers a huge population (everyone who ever received psychiatric treatment) and it extends back to 1970. Studies that extend that far back in time are exceedingly rare.
Denmark is one of the top sources of epidemiological health data as the result of a commitment to collect data that can be used to improve health care treatment.
We Know Relatively Little about Long Term Effects of Drugs
A “long term” study of a drug in the United States is typically a one year study and for most drugs that is the extent of our knowledge, unless someone notices something unusual in the voluntary reports of adverse effects that are submitted to the FDA.
In other words, we know relatively little about the long term effects of most medications in use in the United States.
It is thus particularly reassuring to have this type of high quality data on the effects of lithium.
Findings from the Registry
There have been some surprising findings….
Whereas there is clearly some increased risk of kidney disease with lithium, this study suggests that the risk is much lower than previously thought, and that some of the increased risk may be due to a link between bipolar disorder and kidney disease… Lithium and Kidney Disease
In fact, it is not clear that continuing lithium treatment after a diagnosis of chronic kidney disease is made increases the risk of end stage kidney disease. See the article by Kessing below.
Lithium may also be associated with a reduction in the risk of dementia, a risk which is also increased in people with bipolar according to another study by Kessing.
Lithium is more effective than lamotrigine at reducing the risk of a severe bipolar episode (one requiring hospitalization). Lamotrigine is an alternative medication that is often recommended to young people, and while it is not particularly effective at preventing mania, it is thought to be helpful at preventing depression, but lithium was more effective for preventing severe depressive episodes, as well. This is another study by Kessing.
While bipolar disorder increases the risk of osteoporosis, lithium seems to have a significant protective effect.
Kessing, L. V et al. “Continuation of Lithium after a Diagnosis of Chronic Kidney Disease.” Acta psychiatrica Scandinavica 136.6 (2017): 615–622. Web.
Kessing, Lars Vedel et al. “Association of Lithium in Drinking Water With the Incidence of Dementia.” JAMA psychiatry (Chicago, Ill.) 74.10 (2017): 1005–1010. Web.
Kessing, Lars Vedel, Gunnar Hellmund, and Per Kragh Andersen. “An Observational Nationwide Register Based Cohort Study on Lamotrigine Versus Lithium in Bipolar Disorder.” Journal of psychopharmacology (Oxford) 26.5 (2012): 644–652. Web.