Supplementary Material for: Amyotrophic Lateral Sclerosis Incidence and Previous Prescriptions of Drugs for the Nervous System

<i>Background:</i> An increased frequency of psychotic disorders in amyotrophic lateral sclerosis (ALS) families compared to controls has been reported. Aim of our study was to assess the relationship between nervous system drugs prescriptions and subsequent onset of ALS in a large Italian population. <i>Methods:</i> The study population consisted of all subjects over 15 years at the 2001 Italian census, resident in Turin since 1996 (n = 687,324), followed up for ALS occurrence from 2002 to 2014. Exposure to nervous system drugs was measured until 2012, or until 1 year before ALS onset. The association was estimated for ever and cumulative exposure, through Cox proportional Hazards models adjusted for sex, age, education, marital status and drug co-exposure. <i>Results:</i> In the analysis for ever exposure, opioids were significantly inversely associated with ALS risk (hazard ratio (HR) 0.59; 95% CI 0.35-0.97), while antiepileptics (HR 1.35; 95% CI 0.92-2.00) showed a marginally significantly positive association. Examining cumulative exposure, the protective role of opioids associated with more than 4 prescriptions and the risk effect of antiepileptics for over 6 prescriptions was confirmed. <i>Conclusions:</i> The present study revealed associations of ALS onset with previous exposure to opioids, maybe through the activation of δ receptor and σ receptors and antiepileptics, which are novel findings to our knowledge.