What happens if a person does not sleep?

Image of Dr Simon Kyle
By Dr Simon Kyle

Firstly, you will have missed out on one of the biggest benefits of sleep – feeling fresh in the morning!

Secondly, sleep is vital for healthy physical, mental and emotional processing. When we go without sleep, or have insufficient sleep, our bodies struggle to perform to their full potential and, as a consequence, we can expect impairments to our next-day physical and mental performance.

What happens to the body if you don't get enough sleep?
Due to a close link between certain hormones and sleep, not sleeping has the potential to cause imbalances in hormone activity. Human Growth Hormone, for example, peaks during sleep meaning that insufficient sleep may affect growth and cell-repair throughout the body.

In addition to growth, your metabolism may be affected as well. Studies in which healthy individuals have been sleep restricted have shown that there are alterations to hormones involved in the regulation of appetite and an accompanying increase in seeking out food, as well as glucose metabolism.

What happens in the brain when you don't sleep?
Overall, research has suggested that normal functioning is likely to be hindered by loss of sleep. Repercussions such as reduced energy levels with bursts of euphoria, unstable moods and excessive sleepiness during the day have all been observed in people who haven't slept.

Excessive sleepiness can be especially hindering and even dangerous as it tends to be preceded by frequent lapses in focus before individuals fall into a short episodes of sleep, also known as 'microsleeps'. These episodes are a known contributing factor to traffic accidents with drowsy drivers falling asleep at the wheel (Boyle et al. 2008).

Whilst we can recover from not sleeping very quickly, it can have negative long-term consequences for our health. Chronic poor and restricted sleep are known, for example, to be associated with the development of illness, notably cardiovascular disease, diabetes, hypertension and certain types of cancers.

Research on sleep deprivation
The most well known experiment on total sleep deprivation involved a teenager called Randy Gardner, who managed to maintain wakefulness for 11 days. During this period, he experienced problems with his working memory, speech and eventually hallucinations.

It is safe to say that keeping yourself awake long after feeling the pressure to sleep is unwise. Sleeping is not something humans can whether or not to do – it is essential for facilitating normal functioning.


Boyle, L.N., Tippin, J., Paul, A., Rizzo, M. (2008). Driver performance in the moments surrounding a microsleep. Transportation Research Part F: Traffic Psychology and Behaviour, 11(2), 126-136.

Filed under: Sleep science