SMN1 and amyotrophic lateral sclerosis: In addition, the copy number of SMN did not associate with patient survival (Royston-Parmar; SMN1 p = 0.78 and SMN2 p = 0.23) or age at onset (Royston-Parmar; SMN1 p = 0.75 and SMN2 p = 0.63).<h4>Interpretation</h4>In our well-powered study, there was no association of SMN1 or SMN2 copy numbers with the risk of ALS or ALS disease severity.