Too much REM sleep is bad, as is too little

Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in mammals and birds, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream vividly.

The REM phase is also known as paradoxical sleep (PS) and sometimes desynchronized sleep because of physiological similarities to waking states, including rapid, low-voltage desynchronized brain waves. Electrical and chemical activity regulating this phase seems to originate in the brain stem and is characterized most notably by an abundance of the neurotransmitter acetylcholine, combined with a nearly complete absence of monoamine neurotransmitters histamine, serotonin, and norepinephrine.

Regarding your article “Is sleep a ‘magic pill’ for teen wellness in a mental health crisis?” (8 June), sleep research tells us that good sleep isn’t just about getting enough – the right quality of sleep is key. It has long been known that worrying and stress increase the intensity of REM sleep, when most dreaming occurs, causing it to start earlier on in the night and reducing the deep sleep needed to repair the brain and body. If intense dreaming continues throughout the night, the person wakes up feeling exhausted and lacking in motivation, which researchers – and those who have experienced it – know to be the sleep pattern that characterises depression.

However, if insomnia and nightmares prevent REM sleep from doing the job of reducing cortisol stress hormones and calming emotions from the previous day, the brain’s security officer, the amygdala, is left in a heightened state of arousal. Clinical research shows that depriving someone of REM sleep leaves the amygdala 60% more reactive to emotionally charged events. It is unsurprising, therefore, that Denise Pope reports that insomnia in adolescents increases risk-taking behaviour and impulsivity – this would include the impulse to act on suicidal thoughts. Indeed, insomnia is considered by many sleep studies to be the key risk factor that determines whether a person suffering with post-traumatic stress disorder or major depression will experience suicidal thoughts.

So too much REM sleep is bad for us, as is too little. Public health education should seek not only to emphasise the importance of getting enough sleep, but to explain that the stress from unmet emotional needs can cause depression when we have too much REM sleep, or the impulse to act on suicidal thoughts when we don’t have enough.