Depression in MS: The Circadian Connection

Following my MS diagnosis six years ago, I experienced the usual range of emotions: sadness and feelings of loss. Who wouldn’t feel depressed by this news?

Sadness and grief aren’t only normal reactions to an MS diagnosis. Full-blown depression is, itself, a biological symptom of MS as well as a secondary condition (also called a comorbidity).¹

Is depression a result of MS?

I’d been diagnosed with nonseasonal depression years before. It’s impossible to know if it was secondary to MS or its own standalone condition. For me, it matters less than knowing I’ve successfully treated my depression, whatever the cause.

So, I read with interest recently about new research that suggests a relationship between MS and depression may be the product of disrupted circadian rhythms, which can influence nighttime sleep patterns and daytime fatigue.

What are circadian rhythms?

If you’ve ever heard of the “body clock,” then you recognize circadian rhythms at their most basic.

All living things tune their sleep-wake (and other) rhythms to the light-dark cycles of the planet. Human rhythms allow for a 24-hour day that includes an 8-hour rest (sleep) period and a 16-hour active (wake) period.

These rhythms are managed by a main circadian clock called the suprachiasmatic nucleus (SCN), an organ found deep in the brain. All other systems in the body—and all of our individual cells—have their own clocks, as well. They synchronize with the SCN.

Our circadian rhythms help us to maintain overall health. However, when disrupted, different kinds of physical, emotional, and mental imbalances—all which live at the core of chronic illness—may develop.

What’s circadian disruption?

When our environment and/or behaviors interrupt the natural ebb and flow of our circadian rhythms, we can fall into something scientists call desynchrony. That is, our rhythms have become disrupted. Reasons for desynchrony could include:²

• Not keeping a regular sleep schedule (going to bed and rising the next day at around the same time)
• Too much light exposure at night
• Eating large meals too late at night
• Medication side effects (for instance, prednisone can cause insomnia)
• Pain, which can interfere with sleep and cause daytime fatigue
• Untreated anxiety or depression, affecting daytime energy and nighttime sleep, regardless of season

How do circadian rhythms affect sleep and wakefulness?

The circadian system is fairly complex; suffice it to say that it takes cues from our environment (light exposure, meal times, and activity) to determine when we’re awake and when we should be sleeping.

A sophisticated chain of neurochemical events inspired by these cues are what lead us to drowsiness and, eventually, nighttime sleep. A second series of events help us to awaken in the morning.

Chief among these cues is light exposure. Think about it: It’s hard to get good sleep at night in a well-lit space. But it’s also difficult to feel energetic during the day if we don’t experience exposure to light (especially natural light).

The link between depression and circadian disruption

The study I ran across focused on the relationships between circadian disruption (desynchrony), MS and depression.³ The researchers used questionnaires, data from wearable activity monitors and sleep diaries to determine whether 60 people with MS could be categorized “at risk” or “not at risk” for developing depression.

Almost two-thirds of subjects reported poor sleep, and over half reported substantial fatigue. Over half were considered “at risk” for depression.

Most significant was the association they found between fatigue—MS’s most common symptom—and depression. In fact, the odds of having depression were twice as high for those who exhibited circadian disruption, nearly twice as high for those with poor sleep and almost five times higher for those with fatigue.

The researchers confirmed a meaningful link between circadian disruption, poor sleep, fatigue and the development of depression in people with MS.

It’s not a stretch. Problems with MS can interfere with sleep-wake cycles, leading to behavior changes during the day. These might include less physical activity and fewer opportunities for quality light exposure. Both deficits are known to undercut one’s mood.^4,5

What I take away from this research

It makes sense from personal experience. I live in the Puget Sound. Rainy days blended with daytime fatigue and other MS symptoms (pain, digestive problems, cognitive fog) mean I must force myself to go outside to keep my rhythms synchronized.

No doubt my “low mood” days are part of the outcome of disrupted rhythms. It’s why I swear by my “happy light,” even in summer: it delivers a much-needed energy and vitamin D boost which improves both my mood and motivation.

How do you fend off depression while living with MS?