As most new parents can attest, sleepless nights don’t necessarily make the happiest mornings. For this reason, it makes little sense that complete sleep deprivation temporarily alters mood in nearly half of people with major depressive disorder.
Brain scans of volunteers have shown why this might be the case, revealing interesting changes between critical areas of the brain in healthy volunteers and those diagnosed with major depression.
Research led by the University of Pennsylvania in the US used functional MRI to map and measure the brain functions of 54 people with no history of psychiatric or mood disorders and 30 people with major depression.
Of those with no history of depression, 16 were placed in a control group and given a good night’s sleep between tests. For everyone else, with and without a diagnosis, it was a long evening of reading, playing computer games, watching TV … and without closing your eyes. No caffeine, no exercise. Just bored until sunrise.
Because the human brain doesn’t have enough time to rest and refuel, it’s not the most efficient machine. A piece of tissue at the front of our brain called the dorsolateral prefrontal cortex chugs along slowly, making it harder to pay attention.
Not only is our cognition slowed, but also our ability to regulate our emotions as the amygdala — a key component of the limbic system — works overtime, particularly in response to negative stimuli. Without the prefrontal cortex to rein in our thinking, we can become snappy and irritable.
However, since the beginning of psychiatric research, sleep deprivation has been viewed as a potential treatment for relieving depression, at least in a subset of individuals who experience it as an ongoing mood.
In fact, the researchers behind this latest research found an improvement in mood after the sleepless night in 13 of the 30 patients with major depression.
Meanwhile, the results of a mood test in people without depression generally reflected the type of fatigue that most people feel when they lack sleep.
Image data showed a possible explanation for this contrast. Connections between the amygdala and a bridge between the cognitive and emotional regions of the brain called the anterior cingulate cortex appeared to be enhanced in those whose moods were reported to improve, regardless of their mental health.
Even after two nights of catching up on lost sleep, connectivity between the two regions remained relatively strong.
The principle of treating psychiatric disorders through changes in biological rhythms, known as chronotherapeutics, has become a serious area of research, suggesting that a jolt in our internal clocks could in some way reset faulty regulatory processes.
That’s not to say that frequent sleepless nights is necessarily a good idea for everyone, since poor sleep is associated with a higher risk of dementia later in life. When we mess with our body clock, it can affect our health, social life, and work routine.
However, mapping dramatic changes in communication between areas of the brain known to be involved in emotional and cognitive regulation after sleep deprivation could help identify possible mechanisms responsible for at least some cases of depression.
The World Health Organization ranks major depressive disorders as the third largest burden of disease worldwide. Knowing that it’s at least possible to improve connectivity between areas of the brain critical to mood, we might one day find a way to boost the mood of millions of people without giving our brains the benefits of a good night’s sleep gain weight.
This research was published in PNAS.