I understand narcolepsy has been written off as hereditary, but recently, I read something about narcolepsy being caused by factors other than genetics. Is narcolepsy hereditary or not? You see, I had an aunt who had narcolepsy and I can't help but think I am also prone to developing these "sleep attacks".

Here’s this one question about narcolepsy that researchers are taking a long time to provide an answer to. Is narcolepsy hereditary? For about a hundred years since cases of narcolepsy have been reported, no definite causative factor has been identified. It has always been thought to be hereditary but many are not convinced.

Several studies suggest that genetics may have something to do with the development of this disorder, that the defective gene could be transmitted though heredity in an autosomal dominant fashion. It means an individual has a higher risk of developing narcolepsy himself if a close relative is affected with the disorder. However, only about 5% to 10% of documented narcoleptics report having a close relative with narcolepsy. Is narcolepsy hereditary then? Maybe not.

One of the symptoms of narcolepsy is excessive daytime drowsiness, so excessive that you are talking to a narcoleptic one second, and another second, he’s slumped on the table, snoring! Other distinct symptoms of this disorder are cataplexy (sudden loss of muscle tone), hypnagogic hallucinations (vivid dreaming), sleep paralysis, and automatic behavior. Narcolepsy, in laymen’s terms, is sudden sleep attacks at inappropriate times and places, i.e. while eating, driving, or in the middle of a conversation. This is often triggered by intense emotions like sadness, surprise, fear, happiness, etc.

Normally, when we sleep, we go through a series of sleep stages (non-REM stages) before going to the REM stage of sleep, or deep sleep, where dreaming occurs. It usually takes 90 minutes of non REM sleep stages before going to deep sleep. In narcolepsy, the non REM stage is shorter, and in most cases, the REM stage of sleep is immediately achieved. In other words, when the drowsiness becomes uncontrollable, the body immediately goes into deep sleep regardless of time, place or situation.

It was found out that this anomaly is due to the failure of the brain neurons and neurotransmitters to send the proper signals from the brain to the body. The hypothalamus is the part of our brain that regulates sleep and it produces a substance called hypocretin (or orexin). This substance is responsible for stabilizing the activity of the neurons involved in transmitting the signals to the body when it is time to wake or sleep, or when it is time to relax the skeletal muscles in preparation for the dream stage of sleep. Simply put, hypocretin controls our sleep patterns.

Narcoleptics have been found to have very low levels, and sometimes absence, of hypocretin neurons and neurotransmitters. The reason could be genetic, but another angle that experts are looking into is the possibility of an autoimmune response wherein our body’s defense system is attacking our own cells, in this case the hypocretin cells, mistaking it for a foreign body and destroying it. Now, autoimmunity can also be hereditary. So there’s that question again: Is narcolepsy hereditary? I’m sure you are now confused.

Other factors that can contribute to damage or absence of hypocretin are viral infections like mumps and measles, brain injury, changes in hormones (which could explain why most initial narcolepsy attacks happens during puberty), and stress (narcolepsy also seems to be preceded by a very stressful event like death of a loved one, etc.).

Currently, the consensus is that narcolepsy may be due to genetic factors but ongoing research is underway to prove (or disprove) that. So, if you ask me now, “Is narcolepsy hereditary?” I guess, together, we’ll have to wait a little bit longer for the answer.