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Sundown syndrome refers to a specific state of confusion and agitation that shows up sometime between late afternoon and dusk and persists into the evening. For the most part, experts associate sundown syndrome, or sundowning, with dementia.

Scientific research has yet to identify one specific cause of sundown syndrome. One widely accepted explanation suggests the brain changes associated with Alzheimer’s disease, Lewy body dementia, and other types of dementia can affect circadian rhythms.

This disruption to the biological clock alters normal sleep-wake cycles and triggers evening confusion and distress.

To date, no research specifically links sundowning to bipolar disorder. That said, plenty of evidence does link bipolar disorder to circadian rhythm dysfunction and related sleep disruptions.

Without a doubt, an irregular biological clock can affect the amount of sleep you get, not to mention its quality. But can it also cause evening confusion, disorientation, and other symptoms similar to sundown syndrome?

Read on to learn more, plus get some tips to cope and get support.

Among people with dementia, sundown syndrome is fairly common, though not everyone will experience it.

This late-day confusion can involve:

  • hallucinations
  • verbally and physically aggressive behavior
  • anxiety or irritability
  • suspiciousness or paranoia
  • restlessness or pacing
  • wandering
  • difficulty sleeping
  • lack of interest in listening to suggestions or cooperating with loved ones and other care providers
  • disorientation or loss of focus

While these symptoms don’t show up at any set time — say, 4:30 p.m. — experts generally agree they appear sometime between late in the afternoon or early in the evening. In other words, when the sun goes down.

If you (or a loved one) live with bipolar disorder, many of these symptoms may sound pretty familiar. With bipolar disorder, though, symptoms can develop at any time of day. They won’t necessarily follow any set schedule.

Experts have yet to identify a bipolar-specific sundown syndrome. Still, the condition affects everyone differently, and you could absolutely notice more symptoms, or worsened symptoms, in the evening hours.

This increase in evening symptoms may happen for a few different reasons.

Body clock dysfunction

Researchers have long recognized disrupted circadian rhythms as a key characteristic of bipolar disorder.

The circadian rhythm, in basic terms, is the internal cycle that helps regulate various brain and body processes.

This cycle, which aligns with Earth’s 24-hour day, is very responsive to changes in light. That’s why you feel tired at night, when it begins to get dark, and more alert in the morning, when the sun comes up.

Yet most people with bipolar disorder experience altered sleep-wake cycles. In fact, some experts consider circadian rhythm dysfunction a key component of the condition, not to mention a major cause of sleep problems.

Not getting enough sleep on a regular basis can also lead to:

  • trouble focusing or thinking clearly
  • irritability
  • anxiety

These effects can show up throughout the day, but you could notice them more readily as the day wears on and you feel increasingly tired.

Evening chronotype

Do you consider yourself a night owl?

Some research suggests a link between “eveningness,” or evening wakefulness, and mood-related mental health conditions like bipolar disorder.

Eveningness, in short, means you favor going to bed later and sleeping in over an “early to bed, early to rise” approach.

You might burn the midnight oil because you naturally feel more energized and alert in the evening. Still, staying up late might prove less than ideal when you still have to wake up at a specific time, since this can prevent you from getting the sleep you need. Some evidence also links eveningness to more severe symptoms of depression.

It’s worth considering, too, that you might simply be more attuned to changes in your mood and other bipolar symptoms when you feel most alert — in the late afternoon and early evening.

If everyone around you seems relaxed, calm, and ready to wind down, any irritability, anxiety, or restlessness you experience might stand out even more.

On the flip side, you might also feel restless or anxious if the approaching evening brings feelings of distress. If you dislike night, for whatever reason, this sense of disquiet could worsen your mood, especially when you can’t find relief in sleep.

Medication side effects

Bipolar medications can do a lot to improve symptoms and help reduce mood episodes.

Still, like most medications, they do carry some risk of side effects, some of which may resemble sundowning symptoms.

No clear-cut evidence links evening symptoms to bipolar medications, but a few possible links exist:

  • Agomelatine, a medication that binds to melatonin receptors, may help stabilize circadian rhythms, but limited evidence suggests it might prompt symptoms of mania or hypomania in some people taking lithium for bipolar II.
  • Lamotrigine (Lamictal) can help reduce mood episodes. Anxiety and sleep problems number among its commonly reported side effects, but some people also report more serious effects, including restlessness, anger and irritability, and aggressive behavior.
  • Some people taking lithium, a medication commonly prescribed to treat mania, report problems with memory, concentration, and mental sharpness.
  • Some atypical antipsychotics and antidepressants used to treat bipolar disorder work by blocking the neurotransmitter acetylcholine. These medications could, in some cases, lead to side effects like confusion and problems with memory, concentration, and attention.

Keep in mind, though, there’s nothing saying these symptoms always show up later in the day. But if that’s when you tend to notice them, sundowning might sound like the best way to describe your symptoms, even if that’s not what’s actually going on.

Bipolar subtype

Different types of bipolar disorder exist, and these subtypes can involve different symptom patterns.

Bipolar with mixed features involves a combination of manic and depressive symptoms in the same mood episode. Mania might leave you needing little sleep and feeling more alert than usual, while depression might provoke irritability or anger, restlessness, and trouble concentrating.

If you’ve never had a mixed episode before, you might feel disoriented and confused, not to mention distressed, by the unusual symptoms.

With rapid cycling bipolar disorder, your mood could shift over the course of the day. When symptoms of depression or psychosis, including irritability, paranoia, or disorientation, come on in the evening hours, they can closely resemble sundowning symptoms.

There’s also late-onset bipolar disorder to consider. Bipolar mood symptoms often begin by early adulthood, but the condition can show up for the first time in later life. That means older adults can develop the condition alongside dementia and experience symptoms of sundowning as well as mood episodes.

Therapy, medication, or a combination of the two tend to have the most benefit for improving symptoms of bipolar disorder.

Still, plenty of lifestyle changes can make a difference, too. The tips below may be particularly helpful for symptoms that seem to worsen as night falls.

Keep a consistent schedule

Routines and activities that change from day to day can affect your circadian rhythm and lead to an irregular sleep-wake cycle.

Maintaining a consistent schedule can help regulate your internal clock and improve your sleep as well as your mood. As much as possible, try to stick to a set timeline for:

  • getting up in the morning
  • meals
  • starting and finishing work
  • physical activity
  • relaxation and hobbies
  • going to bed at night

Even making a few changes where possible can help. Maybe your job requires you to work varying hours, and there’s nothing you can do about that. You could, however, try waking up and going to sleep at the same time each day, instead of sleeping in when you have later shifts.

Exercise

Regular physical activity can help restore a consistent circadian rhythm, plus:

If you’re able to exercise, current guidelines suggest aiming for about half an hour of physical activity most days of the week.

Tip: Consider a morning or afternoon walk, bike ride, or hike to reap the added benefits of nature and natural light.

Follow natural patterns of light and dark

You can use daylight to switch back to a 24-hour sleep-wake cycle:

  • Open curtains or spend a few minutes outside after you wake up to catch some sunlight.
  • Try to get some time outside during the day to remind your body it’s daytime.
  • Turn on lights indoors on rainy or overcast days.
  • In winter, when night falls early, use indoor lighting to stay alert and awake.
  • Dim lights and turn off screens when you’re ready to wind down for bed — usually about an hour or two before bedtime.

You can also try light therapy to boost natural light exposure during the winter months, or if you don’t get a lot of sunlight where you live.

Start a wind-down routine

An ideal bedtime routine typically starts long before the clock informs you it’s time to dive under the covers.

Swapping stimulating activities — think loud music, intense workouts, or flashy video games — for more soothing ones can help your brain ease into bedtime mode.

Consider these relaxing activities in the hours before bedtime:

Picking up a few calming hobbies can help relieve stress, which could improve mood symptoms while helping you feel more ready for sleep.

Take it further: Transform your room into the perfect sleep environment.

In almost all cases, bipolar disorder requires professional treatment.

While you can take steps to reduce mood episodes and ease symptoms on your own, support from a trained mental health professional is usually key to lasting improvement.

If you believe you could have bipolar disorder, connecting with a therapist as soon as possible can put you on the path to exploring effective treatment options and getting relief. Therapists can also offer more guidance on navigating sleep problems and other nighttime distress.

Reaching out to a therapist becomes even more important if you notice unusual evening wakefulness along with fogginess and difficulty concentrating, restlessness, irritability, or any mix of mania and depression. Mixed mood episodes are serious, so it’s best to get help right away.

Already working with a therapist? Don’t hesitate to mention any changes in the pattern of mood episodes, such as symptoms that suddenly get worse at night. Your therapist can help you identify possible causes and consider alternate approaches to treatment, if needed.

Experts still have more to learn about the causes of bipolar disorder and how it affects sleep-wake cycles.

Circadian rhythm disruptions could very well factor into symptoms that seem to get worse at night, but other factors might also play a part.

It’s always worth mentioning any new or unusual symptoms, including changes in when they appear, to your therapist or other healthcare professional.


Crystal Raypole writes for Healthline and Psych Central. Her fields of interest include Japanese translation, cooking, natural sciences, sex positivity, and mental health, along with books, books, and more books. In particular, she’s committed to helping decrease stigma around mental health issues. She lives in Washington with her son and a lovably recalcitrant cat.