Pulling an all-nighter can lead to people feeling happy and giddy, a new study suggests.
Sometimes, although the body is physically exhausted, the brain feels slap-happy and loopy – that tired and wired feeling that some people will be familiar with.
Experts say this could be down to the brain chemical dopamine, which plays a role in pleasure and reward.
We found that sleep loss induces a potent antidepressant effect and rewires the brain— Professor Yevgenia Kozorovitskiy
According to the researchers, the effect of missing a night’s sleep is like a potent antidepressant that keeps the mood going for several days.
In the study, mild and acute sleep deprivation was induced in mice before their behaviour and brain activity was analysed.
Not only did dopamine release increase during the acute sleep loss period, synaptic plasticity (the ability of neurons to modify their connections) was also enhanced – literally rewiring the brain to maintain the bubbly mood for the next few days.
The findings, from neurobiologists at Northwestern University, could help scientists better understand how moods naturally change.
They could also lead to a more complete understanding of how fast-acting antidepressants such as ketamine work and help researchers identify previously unknown targets for new antidepressant medications.
Author Professor Yevgenia Kozorovitskiy, said: “Chronic sleep loss is well studied, and its uniformly detrimental effects are widely documented.
“But brief sleep loss — like the equivalent of a student pulling an all-nighter before an exam – is less understood.
“We found that sleep loss induces a potent antidepressant effect and rewires the brain.
“This is an important reminder of how our casual activities, such as a sleepless night, can fundamentally alter the brain in as little as a few hours.”
But the researchers warn against starting to pull all-nighters in order to brighten a blue mood.
Prof Kozorovitskiy said: “The antidepressant effect is transient, and we know the importance of a good night’s sleep.
“I would say you are better off hitting the gym or going for a nice walk. This new knowledge is more important when it comes to matching a person with the right antidepressant.”
The researchers found that after a sleepless night, the behaviour of the mice shifted to become more aggressive, hyperactive and hypersexual, compared to animals that experienced a typical night’s sleep.
The activity of dopamine neurons, which are responsible for the brain’s reward response, was measured, and researchers found activity was higher in animals during the brief sleep loss period.
They also discovered that the antidepressant effect persisted, except when dopamine reactions were silenced in the prefrontal cortex – the front of the brain
Prof Kozorovitskiy said: “That means the prefrontal cortex is a clinically relevant area when searching for therapeutic targets.
“But it also reinforces the idea that has been building in the field recently – dopamine neurons play very important but very different roles in the brain.
“They are not just this monolithic population that simply predicts rewards.”
Most of the behaviour, such as hyperactivity and increased sexuality, disappeared within a few hours after acute sleep loss, but the antidepressant effect lingered for a few days, the study published in the Neuron journal found.
