It is an unfortunate reality that the vast majority of medical professionals cannot name the 6 main symptoms of narcolepsy. This goes a long way towards explaining why the average diagnostic time for narcolepsy is still measured in years rather than months and why it is often misdiagnosed or undiagnosed indefinitely. It is important that people affected by narcolepsy, or who suspect that they or their loved ones might be suffering from narcolepsy, know what the symptoms are and can explain them to others in a clear and easily understood manner. To allow us to do this Narcolepsy Ireland has devised the following memory aid.

This is a useful memory aid which will help people easily remember the main symptoms of narcolepsy. If you remember the words “HIS ACE” then you have the first letters of the 6 main symptoms of narcolepsy type 1. 

The “HIS” deals with the symptoms which are mainly associated with night-time. The “ACE” deals with the symptoms which are mainly associated with daytime.

Note: While these are the main six symptoms of narcolepsy, and are the ones which should alert any diagnostician to the possibility of the person having narcolepsy, there are many other symptoms of this disease which are discussed in other sections of this website.



H - Hallucinations

I - Interrupted night-time Sleep

S - Sleep paralysis

A - Automatic behaviour

C - Cataplexy

E - Excessive daytime sleepiness



These are typically experienced while falling asleep or waking up and are often described as extremely vivid dreams that are indistinguishable from reality. The key feature of these hallucinations is that the person experiencing them feels that they are actually real life. This can be extremely disturbing and frightening for adults and particularly terrifying for children. It is believed by many authorities that this phenomenon is caused by the almost immediate onset of REM sleep in persons with narcolepsy. Hallucinations which occur  when falling asleep are known as “Hypnagogic hallucinations” and those that occur when waking up are known as “Hypnopompic hallucinations”.


Interrupted night-time sleep

Contrary to the common misconception that sufferers of narcolepsy sleep long and soundly, the actual reality is that their night time sleep is of extremely poor quality and is interrupted, disrupted and punctuated by continuous wake / sleep periods and that it does not include any significant periods of the deep restorative sleep that non sufferers have. The consequence of this is that the PWN feels in the morning as one would feel if one had little or no sleep at all - in other words, totally exhausted.

 Very poor quality, continually interrupted night-time sleep is one of the key features of narcolepsy. It is worth stressing this fact because the average person who has any knowledge of narcolepsy at all will almost always feel that narcolepsy involves long periods of sleep which they equate with peaceful rest.

 The most common misunderstanding of narcolepsy is that it simply means that the person who suffers from narcolepsy sleeps a lot more than normal. This has led to  narcolepsy being seen as an almost enviable trait and to it being treated in films and other media as a bit of a joke. We should be able to explain to people who innocently hold this belief that narcolepsy is very far from being a joke.


Sleep Paralysis

This is usually confined to times when the sufferer is waking up or going to sleep. Although still awake and fully conscious, the person finds they cannot move. This can be very frightening and can last for seconds or for as long as several minutes. The fact that interrupted night-time sleep generally involves the sufferer waking on multiple occasions through the night means that they can have  multiple experiences of sleep paralysis every night. It is believed by that this phenomenon is caused by the onset of the normal muscle paralysis associated with REM sleep occurring while the person is still awake. It is similar in this regard to one of the other main symptoms of narcolepsy, which is cataplexy.


Automatic Behaviour
Automatic Behaviour is one of the classic symptoms of narcolepsy. Automatic behaviour is manifested by the person with narcolepsy continuing to perform an activity that they are engaged in but without any awareness or memory of actually carrying out that activity. An example might be when they are writing in a normal coherent way and then move into automatic behaviour and continue  to write in a totally non-coherent way, their perfectly normal writing style changing to an incomprehensible scrawl. Or the person may find themselves in a different room in their house without any recollection of how they got there. Automatic behaviour happens as the PWN is hovering between being awake and being asleep.


Cataplexy is one of the classic symptoms of narcolepsy. Cataplexy is considered an extremely specific marker for narcolepsy. There are no other known diseases of which  cataplexy is a symptom.  Not all PWNs will have cataplexy. Estimates vary, as the statistics are notoriously difficult to pin down due to the poor diagnostic history of narcolepsy, but the current general consensus is that somewhere between 50% to 70% of people with narcolepsy will also have, or develop, cataplexy., i.e they will have type 1 narcolepsy.

  • Narcolepsy with cataplexy is known as “Type 1 Narcolepsy”

  • Narcolepsy without cataplexy is known as “Type 2 Narcolepsy”

Cataplexy is where one’s muscles temporarily lose some or all of their strength, or their ability to function. The most severe form of cataplexy results in the person totally collapsing and being effectively temporarily paralysed for periods ranging from as short as a split second to. as long as several minutes. During this time the person remains  fully conscious but is unable to move or speak. The muscles which control vital bodily functions, heart beating, breathing and so on,  are not affected in any way. There is no residual damage caused to the muscles which are totally as before once the cataplectic episode is over.

 Cataplexy often manifests itself in much less severe ways, such as a fleeting weakness or a momentary loss of grip, causing e.g. a cup to slip from one’s grasp - and consequently is very often misdiagnosed or undiagnosed and passed off as clumsiness. Cataplexy can vary in severity from total collapse to something  as simple as a slight lolling of the head, or the droop of an eyelid.

What causes cataplexy?

Cataplexy is usually triggered by instances of strong emotions, such as laughter, excitement, anger, fear and so on.

But why?
The REM  periods of the normal sleep cycle are when we dream. To prevent us from physically acting out our dreams in our sleep by actually moving our arms and legs and our body in a way that mimics what we are doing in our dream, during REM periods the brain actually paralyses the body so that it cannot move during the dream. This temporary paralysis is totally normal and protects us from harming ourselves (or others) when we dream. In cataplexy, this paralysis, full or partial, occurs when the person is awake. It can last for as long as a split second to as long as several minutes. The consequences are often extremely distressing and can in some cases be life threatening, e.g. while driving. The frequency of cataplexy in PWNs can vary tremendously, occurring as few as one or two instances a year to multiple times per day.


Excessive Daytime Sleepiness
Excessive Daytime Sleepiness, often referred to as EDS,  is one of the classic symptoms of narcolepsy.

EDS manifests itself as periodic, overwhelming, irresistible urges to sleep during the day, often in inappropriate places  and times, such as at work, in school, while driving etc. People have been known to fall asleep while swimming! These episodes of falling asleep can obviously be extremely dangerous for the person involved and sometimes for others, e.g. passengers in a vehicle like a  car or bus. These irresistible sleep periods can last for a number of seconds,  a number of minutes or up to an hour or more.

EDS is very often one of the first symptoms of narcolepsy to appear and is commonly initially ignored as being a real problem at all, even by the person affected. It is frequently misdiagnosed by medical professionals as being due to other factors which can also be associated with fatigue e.g depression, or even lifestyle. The reason that the PWN has these  irresistible urges to sleep are complex but it is now generally agreed by researchers that it is ultimately due to the lack of the normal control of the sleep pattern exerted by the hypocretin neurotransmitter, the absence of which is the fundamental cause of narcolepsy. In more simple terms, undoubtedly one of the main reasons for EDS is because of the extremely poor quality of the PWN’s  night-time sleep, which is again caused by the absence of the controlling neurotransmitter, hypocretin