I am a morning person. I am terrible at sleeping in, and I have probably averaged no more than six hours of sleep per night for as long as I can remember. My parents, also, have always been early risers, and it’s not unusual for the house to fall silent by 10 p.m.

This led me to some questions:

Is our relationship with sleep genetic? Are we born either a morning person or a night owl? Is our sleep pattern a habit we develop over the course of our lives—and if so, can we change it? Or are some people’s brains simply wired toward getting a better night’s’ sleep than others?

Sleep is one of the most essential human activities. It is an automatic, natural state somewhere between conscious and unconscious, and there is not a single cell or tissue in the body or brain that does not benefit from getting a good night of rest. We sleep so that our minds have time to process the billions of emotions, thoughts, feelings and actions that we experience when we are awake so that they can be organized and stored in memory.

So why do some of us find sleep so hard?

1. Genetics

Despite what we might think, less than three percent of us can blame our genes for how easily we manage to sleep. For these people as little as six hours a night is enough to maintain a high level of cognitive function throughout the day. However, for the rest of us, a regular eight hours a night is the recommended sweet spot—getting less than this over a long period of time can be costly.

2. Hormones

Although uncommon, for some people basic physiology is, at least in part, accountable for sleep disturbance. The hormones cortisol and adrenaline trigger a state of alertness and arousal. Unless linked to stress, these hormones are generally released into the brain first thing in the morning, and then in relatively small amounts throughout the day. However, in some cases, the brain receives a consistently high level of cortisol and adrenaline throughout the day and night. The result is a constant state of alertness during the day and night, and when the sleep state is eventually reached, it’s easily disturbed by light, sound or movement.

3. Sleep disorders

Sleep disorders such as sleep apnea; sleep paralysis; snoring; REM sleep disorder and exploding head syndrome are among just a few of the disorders associated with poor sleep. Perhaps one of the more common disorders is sleep-walking.

According to Mark Mahowald, a professor and pioneer of sleep behavior at Stanford University, the root cause of sleepwalking is neurological. Normally as our bodies move in and out of different phases of rest and slumber, the brain stem paralyzes our limbs and nervous system so that we are not disturbed by our own movement. This process is called ‘the switch,’ and for most people, it occurs several times a night without any problems. For some people, however, the switch is prone to error, effectively allowing the body to stay awake while the brain sleeps. During this state, the body is prone to carry out a variety of automatic behaviors that have been ingrained deep inside the brain, while our brains remain oblivious with no conscious awareness of what the body is doing.

4. Sleep terrors

Like sleepwalking, sleep terrors only affect a minority of people but can be highly unpleasant. For someone experiencing a sleep terror, the activity inside the brain is markedly different from when they are awake. During sleep terror, all areas of the brain shut down except for the most primitive areas that control walking, breathing, and basic survival. These areas are separate from regions of logical thought and reasoning that lie unconscious during sleep and can, therefore, operate automatically without conscious awareness. As such, when a sleep terror is triggered it is experienced in the rawest of emotional and imagery form with no chance of logic or reason intervening.

5. Brain development

In addition to common sleep disorders, poor sleep quality has been associated with a number of developmental disorders and learning difficulties. Although it is yet to be determined whether poor sleep is the result of impaired development, or whether the reverse is true, sleep is essential for memory formation and learning, and so when disrupted for prolonged periods of time, the ability to hold and recall information will also be compromised.

6. Habit

Perhaps the most common cause of sleep disturbance comes down to habit. Unlike some of our perhaps more obvious habits, such as a morning coffee, the route we take to work, or the fact we always buy the same foods at the supermarket, we are continually carrying out little subconscious habits without even knowing. These habits are so deeply ingrained in the subconscious areas of our brain that we often don’t realize we’re doing them. Sleep routine is one of these. Hours before we make the decision to go to bed, we start preparing for it. We might subconsciously begin reciting the storyline to ourselves that we won’t get to sleep, or that we will wake several times a night. We might set our alarm early and go to bed believing we will wake several times in the night in anticipation. We might experience poor sleep once a week, then twice, three times, and then anxiety kicks in as we build ourselves up for the struggle. To this extent, our quality of sleep becomes a subconscious decision, one we make before our heads even hit the pillow. We are already setting ourselves up for a poor night sleep—expecting to wake early, fall asleep late or be disturbed every hour.

So, back to me being a morning person. Am I really a morning person or do I habitually struggle to get to sleep only to wake again before 6 a.m.? Or maybe I can thank my ancestors for inherited sleep genes? What we can say is that the ability to get a regular eight hours might be associated with far more than our ability to relax and unwind before our head hits the pillow.