Yes BUT this is only true for type 1 narcolepsy. Scientists now believe that type 1 narcolepsy could be autoimmune in origin due to a gene found in 99% of NT1 patients. (for those interested, HLA DQB1*0602.
For those of us with a type 2 diagnosis, the cause is still unknown. It could be that some of us are in the earlier stages, it could be that there is a different cause altogether. They are rather certain though about NT1.
Hope this helps.