Sleep and depression have one of the most stable relationships in psychopathology and it is estimated that up to 90% of patients with depression also suffer from sleep disturbances, ranging from difficulty falling asleep to early awakenings (onset insomnia) to hypersomnia (excessive daytime sleepiness).
Therefore, due to either too much or too little sleep, almost all people with depression suffer greatly when they go to bed.
This Tuesday is World Day for the fight against depression and the Spanish Sleep Society (SES) is taking the opportunity to warn about this complex pairing and how insomnia affects this mental disorder.
María José Aróstegui is a psychologist and member of the SES Insomnia working group and says that current scientific evidence no longer sees insomnia "only as a symptom, but as a causal risk factor" for depression, so that we are talking about a bidirectional relationship in which sleep problems are both cause and consequence.
In an interview with RTVE Noticias, Dr Ginés Sabater, vice-president of the Spanish Association of Sleep Disorders (ASENARCO), assures that there is a "very clear and, moreover, very well scientifically proven relationship".
"People who suffer from chronic insomnia are more at risk of depression, and in turn, most people with depression have some kind of sleep problem. Poor sleep not only accompanies depression, but can also increase the incidence and prevalence of the disease," he explains, adding: "Depression and insomnia feed off each other: if you don't treat both, you don't cure either.
Lack of sleep affects amygdala regulation
The psychologist points out that people with chronic insomnia have twice the risk of developing major depression compared to those who sleep well, and this is because lack of sleep affects the regulation of the amygdala (the emotional part of the brain): "It makes us more reactive to negative stimuli and less able to process stress, creating the perfect breeding ground for a mood disorder.
This close relationship, explains the SES spokeswoman, has a neurobiological explanation as both disorders (depression and insomnia) share the same "pathways in the brain". Thus, the dysregulation of serotonin, dopamine and noradrenaline would affect both mood and sleep-wake cycles, and the stress response system (the hypothalamic-pituitary-adrenal axis) is often overactive in both disorders, "keeping the body in a state of alertness that prevents sleep and depletes emotional resources".
Dr Sabater adds to the same idea, explaining that the neurotransmitters involved in insomnia and depression have common actions: "Serotonin is the precursor of melatonin and both use the same 'raw material', tryptophan, to produce them. We prescribe drugs that increase serotonin in the space between two neurons to treat depression, and that increase causes more melatonin to be generated. The reverse effect, obviously, links low serotonin and melatonin with depression and insomnia.
He adds that depression and insomnia are not just psychological problems, but disorders of neurobiological regulation of the brain and the internal clock.
14% of the adult population has chronic insomnia
Everything becomes more complicated in a society like ours that does not sleep well, with more than worrying general data. According to the Spanish Society of Neurology (SEN), 48% of adults do not get enough quality sleep and 54% of Spaniards sleep less than the recommended number of hours - between seven and nine in adulthood.
The Spanish Sleep Society estimates that 14% of the Spanish adult population, around 5.4 million people, suffer from chronic insomnia. A figure, says the SES, "alarming per se" and even more so if we analyse the impact of chronic insomnia on the physical and mental health of the population.
All this added to a consumption of benzodiazepines that places Spain among the world's leading countries and with an absolute normalisation of bad sleep.
The sleep structure of a person with depression is that of a lighter and more fragmented sleep, as the president of ASENARCO explains: "We are basically talking about two types of insomnia: the insomnia of conciliation, where the person finds it difficult to start sleeping, usually waking up more during the night and not being able to sleep again, and the insomnia of early morning, with the typical early awakening, waking up too early without being able to go back to sleep".
In addition, he adds, there are changes in REM sleep (deep sleep): it usually comes earlier than normal and more intensely in the first part of the night and the result is not very restful sleep, even if the person spends many hours in bed.
Depression is relieved if insomnia is treated
The psychologist Aróstegui says that the idea that sleep is not a passive state, but an active process of brain cleansing and emotional regulation, is increasingly permeating society. However, in her opinion, there is still a lack of understanding that "taking care of sleep is, literally, preventive medicine in mental health".
The Spanish Sleep Society says that recent clinical trials show that in patients with depression, when insomnia is specifically treated, depression remission rates are twice as high as in those who receive only mood treatment.
Scientific evidence demonstrates this with trials pointing to improvement in patients with depression when they undergo cognitive behavioural therapies for insomnia.
He adds that scientific evidence warns that insomnia often acts as a residual symptom. "If depression improves, but insomnia persists as a residual symptom, the risk of relapse is very high.
Sabater explains that for years it was thought that 'if we cure depression, sleep becomes normal', but the truth is that "insomnia is an independent disorder and in 40-80% of patients with depression, insomnia persists, even if the mood improves". Poor sleep is a risk, chronification and relapse factor for depression. "Treating depression without treating insomnia is accepting an incomplete cure," he adds.
The doctor points to behavioural and educational measures for the treatment of insomnia - as a basis, cognitive behavioural therapy for insomnia (CBT-I) - and, secondly, drugs, which can be used "well prescribed by the doctor, but with a clear plan, limited time and check-ups".
Finally, ASENARCO also advocates a "much needed" improvement in the 'sleep culture' in our country and recalls that the WHO points to the three basic pillars for a healthy life: diet, exercise and sleep.
In this sense, Sabater warns: "We have normalised little and bad sleep as if it were part of modern life, but sleep is a biological pillar of health. Better sleep culture means education from an early age, habits consistent with light and schedules, and understanding that sleep regulates emotion, memory, energy and mental health. Without such a culture, we arrive late when the problem is already chronic.
A poor relationship with sleep can start with a one-off event - stress, bereavement, a change of job - but if it continues for weeks or months, the brain learns the pattern and insomnia sets in.
Practical guide to good sleep: how many hours?
-Newborns (0-3 months): Between 14 and 17 hours.
-Babies (4-11 months): Between 12 and 15 hours.
-Children (1 and 2 years old): Between 11 and 14 hours.
-Children (3-5 years): Between 10 and 13 hours.
-Children (6-13 years): Between 9 and 11 hours.
-Adolescents (14-17 years): Between 8 and 10 hours.
-Young people (18-25 years): Between 7 and 9 hours.
-Adults (26-64 years): Between 7 and 9 hours.
The sleep decalogue
-Establish fixed bedtimes and wake-up times.
-Respect the hours of sleep.
-Look for sunlight when you get up.
-Exercise at least 30 minutes a day.
-Dinner, two hours before bedtime.
-Avoid long naps longer than 20 minutes.
-Avoid electronic devices at least two hours before bedtime.
-Organise your bedroom with separate areas for work, study and leisure.
-Avoid stressful activities before going to bed.
-If you are a smoker, quit.
SOURCE: ASENARCO
Source: A European Perspective, RTVE
Originally published by María Menéndez on 13 January 2026 08:25