Are Poor Sleep Habits Fueling Your Depression?
What Is the Body Clock?
Your body clock (also known as your internal clock or biological clock) is an internal timing function that controls the body’s cycles or circadian rhythms. Found in almost every organ or tissue, the body clock is made up of a master clock in the brain containing over 20,000 neurons that communicates with internal clocks in cells throughout the body. With input from the body clock, circadian rhythms follow a 24-hour cycle that is highly dependent on lightness and darkness.
The biological clock and circadian rhythms are involved in several functions including:
- Sleep-wake cycle
- Mental alertness
- Brain-wave activity
- Cell regeneration
- Heart functioning
What Disrupts Your Body Clock?
Your inner clock is very sensitive and can be impacted by a number of common occurrences.
Smartphones and Laptops
Research ties smartphone use before bed to poor sleep. Devices like mobile phones, tablets and laptops have powerful lights that are so akin to daylight they can trick your inner clock into thinking night is day. This can disrupt the body’s production of melatonin, the sleep hormone that helps you catch good-quality Z’s.
Drug and alcohol abuse and disruptions to circadian rhythms have been well-documented and is even an issue often tackled in drug rehab. Some researchers theorize a bidirectional relationship between substance abuse and body clock interruptions. This means alcohol addiction and drug abuse may lead to sleep disruptions, and sleep disruptions may grease the wheels for addiction relapse.
Watching TV right before bed can negatively impact sleep in similar ways as laptops and smartphones. Televisions emit the same type of blue light that can halt melatonin. Even if you find television doesn’t stop you from falling asleep, it can cause poor quality of sleep by delaying REM sleep.
Termed “shift work sleep disorder (SWSD)” by scientists, if you work nights, your circadian rhythms get interrupted, putting you at risk for excessive sleepiness and insomnia. Research shows that people with SWSD have much higher occurrences of depression, ulcers, absences from work, family and social activities, and accidents related to lack of sleep.
Traveling to different time zones causes an imbalance in the 24-hour cycle your biological clock follows. Your inner clock stays synced with your usual time zone for several days before adjusting to the new one.
As you age, your biological clock changes too. This explains why Grandma is always the first one awake, catches the early bird special and retires early in the evening. One study examined 150 brains of elderly people and the 235 genes that make up the master body clock. It found that loss of circadian rhythm later in life might explain changes in mood, cognition and sleep late in life.
Daylight Savings Time
“Springing forward” can even tease your internal clock. Some research found that your body clock doesn’t adjust to the one on your nightstand every spring when clocks move forward an hour. Your body clock draws on daylight to sync up with the seasons and daylight savings time interferes with this process. One study found that more people were admitted to ERs for strokes during the two days following daylight savings time, especially those already struggling with conditions like cancer.
Study Links Depression and Body Clock Disruption
A recent study by University of Glasgow researchers found a potential tie between disruptions to the biological clock and mood disorders like depression and bipolar disorder. Smaller studies have found similar correlations, but this was the largest of its kind. Here are the main takeaways:
- 91,105 study participants ages 37-73 wore activity monitors for one week to gauge rest-activity rhythms (relative amplitude), which charted body clock disruptions.
- Disruptions were classified as inactivity during the day and high activity late in the evening.
- Researchers compared participants’ disruption data to their answers on questionnaires designed to assess well-being, cognitive function and mental illness symptoms.
- Researchers compared data from participants that reported “normal” activity (activity during the day, inactivity at night) with those that experienced body clock disruptions.
- Results were adjusted for potential biases like gender, age, lifestyle, childhood trauma and education.
The UK study found participants that experienced more body clock disruptions were 6 to 10% more likely than those who didn’t to exhibit symptoms consistent with a mood disorder diagnosis. Participants with body clock disruptions were also more likely to report loneliness, lower well-being, slower reaction time, more mood swings and neurotic tendencies, and less joy.
In a University of Glasgow press release, lead study author Dr. Laura Lyall said, “We found a robust association between disruption of circadian rhythms and mood disorders. Previous studies have identified associations between disrupted circadian rhythms and poor mental health, but these were on relatively small samples.”
Body Clock Disruptions or Depression: Chicken or the Egg?
What remains unclear is whether mental health disorders like depression cause body clock disruptions or the disruptions cause depression. Conditions like insomnia, poor sleep-wake cycles, low energy and grim outlooks are also common symptoms of depression. Though the UK study found an undeniable link between biological clock disruptions like sleep disturbances and mental health issues, it could not determine which condition came first.
The researchers acknowledge the limitations of their study as observational associations and not cause-and-effect relationships. “Our findings indicate an association between altered daily circadian rhythms and mood disorders and wellbeing”, Dr Laura Lyall said in the university press release. “However, these are observational associations and cannot tell us whether mood disorders and reduced wellbeing cause disturbed rest-activity patterns, or whether disturbed circadian rhythmicity makes people vulnerable to mood disorders and poorer wellbeing.”