Recent research demonstrates that patients with amyotrophic lateral sclerosis (ALS) have a higher risk of developing depression, both immediately before and after being diagnosed with ALS.
While the study, “Depression in amyotrophic lateral sclerosis,” which appeared in the journal Neurology, could not state exactly how or why the two diseases are linked, it suggested that the findings may influence how clinical trials are designed because depression may impact whether patients are willing to participate in studies.
Researchers at Karolinska Institutet in Sweden pulled data from health and population registries to identify 1,752 patients with ALS, diagnosed between July 2005 and December 2010. For each patient, five control individuals (study participants without ALS) of the same age, sex and region of residence were included, totaling 8,760 controls for the study. Including a control group in a study such as this one allows researchers to obtain more conclusive results.
The research team looked at a period of one year preceding ALS diagnosis in participants to identify diagnoses of depression or antidepressant use. Analyses showed that patients with ALS had a 3.5-fold higher risk of depression compared to controls in the year before diagnosis.
Looking at the results in another way, depressed patients had a 3.6-fold higher risk of developing ALS within a year. As the period between depression and ALS grew longer, the risk of developing ALS decreased, with only a 0.9-fold increased risk if depression was diagnosed three years before ALS.
A similar pattern was seen when researchers used antidepressants as a proxy for disease. Antidepressants were used more often by ALS patients than controls. In the year before ALS diagnosis, there was a 5.8-fold higher likelihood of using antidepressants. During the year after, the risk increased to 16.1-fold compared to controls.
The team also followed patients who had been diagnosed with ALS, but did not yet have a depression diagnosis. During the first year after an ALS diagnosis, the risk of depression was 6.7-fold higher than in controls. The risk dropped off during the second year after the diagnosis.
When researchers adjusted the analyses for other factors that might have influenced the results, such as education and socioeconomic status, the results remained unchanged.
Since the study observed only the appearance of the two diseases, researchers are unable to say if depression may be an early sign of ALS, or a result of psychological distress linked to getting ALS. There also is a possibility that cognitive problems linked to ALS may be wrongly classified as depression.