[Originally written and published in May, 2016]
At Papworth Hospital being evaluated for sleep dysfunction in October, 2017.
Ideally, a good night’s sleep restores the mind and the body, preparing us for the next day; without it, our mood and mental performance are affected (Palagini & Rosenlicht, 2011). Sleep is also linked to learning, healthy child development, consolidation of long-term memory, and medical health (Maquet, 2001; Walker & Stickgold, 2004; Gais et al., 2006; Harvard Medical School, 2008; Palagini & Rosenlicht, 2011; Wilhelm et al., 2013; Xie et al., 2013).
Despite these benefits, the exact role of sleep, and especially the role of dreaming, remains elusive.
Many ideas about the source and purpose of dreams have emerged over the centuries. These are depicted in the arts, in literature, and in philosophical writings. Across cultures and throughout human history, we have given dreams supernatural meaning: using them to predict the future and seeing them as Divine manifestations communicated by gods to mortal men (Palagini & Rosenlicht, 2011). More recently, dreams became a focus for psychoanalysts, who believed that dreams provided insight into our unconscious minds and emotions (Palagini & Rosenlicht, 2011).
At some point, there was a shift from the interpretive nature of dream analysis to a focus on the neurology and the cognitive processes involved. The question became: what is the psychological nature and function of dreams?
Modern psychology links dreaming with learning, intelligence, mood regulation, and emotional well-being (Beauchemin & Hays, 1996; Mallon, 2002; Agargun & Cartwright, 2003; Zhang, 2009).
Evidence suggests that dreaming is also linked to depression.
Those with depression can experience a range of sleep abnormalities from over-sleeping and over-dreaming, to insomnia and being less able to recall dreams. While exploring this association, I came across this: a UK website aimed at helping people understand and treat depression.
According to this website, depressed people dream almost three times more than clinically normal people because of emotional arousal and unresolved worry. It claims that an increase in dreaming means a decrease in restorative deep sleep. This leads to an exhausted brain and body, accounting for many of the symptoms of depression, including feeling low, tired, and emotional, and having a lack of motivation.
The logic is that unresolved emotions and thoughts get “dreamed out” during sleep. This allows us to deal with the next day’s events. While dreaming, we often have more stress hormones, such as adrenaline, in our systems. Over-dreaming strains this system, leaving us exhausted when we awaken.
This is something I can relate to. I often wake up feeling no more rested than when I went to bed, and waking from vivid dreams is a common experience. In fact, I can’t think of a time I have ever woken up and not been dreaming. [2021 update: a year and a half after writing this post, my sleep state was evaluated (picture above) and it turns out that I have a sleep disorder -- parasomnia overlap -- so it's likely that I'm not a good example of the typical experience of dreaming with depression. Or maybe I am. Who knows?]
And so, this website triggered an investigation, to see if sleeping and dreaming patterns could help explain depression, or even help resolve symptoms.
Before I discuss this, though, let’s get a quick overview of sleep physiology:
Normally, human sleep is characterised by 90-minute cycles of two qualitatively different brain states: rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep.
NREM sleep consists of four stages: Stage 1 is the lightest sleep and Stage 4 is the deepest. Stages 3 and 4 are sometimes called “slow wave sleep” or “delta sleep”.
REM sleep is sometimes called “paradoxical sleep” because it resembles active wakefulness in terms of the brain’s electrical activity, but it occurs without the ability to move major muscle groups. Sleep walking occurs when your body hasn't been paralysed during this stage of sleep.
Contrary to popular belief, “REM sleep” and “dreaming” are not synonymous; both REM and NREM sleep are closely linked to dreaming. In fact, REM and NREM dreams are often indistinguishable. However, dreams occurring during NREM sleep are typically less elaborate, involve less visual imagery and participation, tend to be less bizarre, and are less likely to be remembered (Palagni & Rosenlicht, 2011).
Additionally, REM sleep more than NREM sleep impacts next day emotion and mood (Vanderkerckhove, & Cluydts, 2010), which brings us back to the main topic: the link between dreaming and depression:
We are usually able to regulate negative mood overnight by dreaming, which helps us play out the waking introspections we have but don’t act upon when we are awake (Beauchemin & Hays, 1996; Aguran & Cartwright, 2003). Normally, negative dreams occurring early in the night reflect this mood-regulation process. Negative dreams occurring later in the night suggest a failure to complete this mood-regulation process – a feature of depression (Agargun & Cartwright, 2003).
Disordered and non-restorative sleep is one of the primary features of depression. In particular, depression is characterised by reduced slow-wave sleep and alterations in REM sleep.
This includes early onset of REM sleep, an increase in the amount of REM sleep in one night, and more eye-movement during REM sleep (Beauchemin & Hays, 1996; Cartwright et al., 1998; Palagni & Rosenlicht, 2011; Tribl, 2013).
Interruptions to REM sleep can even ease depression and increase energy. This is especially true for “evening types” (Cartwright et al., 1998; Vanderkerckhove, & Cluydts, 2010). While most people experience a reduction in mood following sleep deprivation, many of us with depression report a positive change in mood. However, the improvement is short-lived, and depression re-emerges after the following night (Cartwright et al., 1998; Vanderkerckhove, & Cluydts, 2010).
Let's insert drugs into the discussion (prescribed drugs):
As with selective REM-sleep deprivation, anti-depressants can help alleviate depression by reducing REM sleep and dreaming (Tribl et al., 2013). Unlike sleep deprivation, the benefits of anti-depressants are longer-term.
However, anti-depressants can also have adverse effects on sleep. For example, SSRIs (a common group of anti-depressants and usually the first category of anti-depressants that a person will be prescribed) can cause insomnia, reduce total sleep time, and even increase the frequency of nightmares (Tribl et al., 2013).
Meanwhile, if the website I mentioned earlier is correct, and REM-sleep dreaming helps reduce worry, do we increase anxiety by decreasing depression in this way? Studies show that anxiety in response to stressful stimuli increases after a person is deprived of REM-sleep (Vanderkerckhove, & Cluydts, 2010). This means that, according to my own logic at least, even if changes in REM sleep, aided by anti-depressants, reduce depression, anxiety could be increased.
But then, why would some SSRIs also be prescribed to alleviate anxiety? Clearly, I don't know enough about the subject to answer this question, let alone articulate how it works.
So, now I'm relying on my own speculation: maybe SSRIs help limit the anxiety we experience to anxiety that is caused by everyday (external) situations, by reducing only trait (internal) anxiety, like panic disorder or generalised anxiety disorder.
Anxiety caused by external situations is what I would call “stress”. The function of dreams for reducing this stress might be dependent on other factors, like the dreamer's circumstances, experiences, or social network. That is, we might need to rely less on REM dreaming to deal with everyday, externally-caused anxieties, if we are able to rely more on cognitive coping strategies and other forms of emotional regulation.
This suggests that we should equip people with life skills and techniques for reducing everyday stresses. This may be in combination with sleep-related strategies (whether medicinal or not) for dealing with depression and trait anxiety.
To summarise [TL:DR]
Depressive thinking causes emotional arousal. This may cause over-dreaming (or even nightmares), making a depressed person more exhausted the next day and less able to cope. The drugs that help many people deal with depression might also make us less able to cope with stressful situations -- if I have understood what I have read correctly. This is because a reduction in REM sleep also means a reduction in our ability to dream out everyday stresses or to confront emotions.
Beyond this reasoning, and the academic papers that I read and attempted to piece together for this blog post, I uncovered as many questions as answers. This leaves my understanding of the relationship between depression, dreaming, and drugs far from complete. Sorry about that.
As is often the case in psychology, things that seem as though they should have a straightforward answer often don't.
I couldn't find definitive evidence or explanations for the relationships between mood-disorders, sleep, dreaming, and anti-depressants. What is clear to me, however, is that sleep and dreaming serve multiple purposes.
Without wishing to over-simplify the answer, I am in little doubt that dreaming and depression are related, most likely due to abnormal REM sleep.
Less clear is the exact nature of the link. Instead, I have a collection of interesting findings and explanations that make understanding the function of dreams just as mystifying as dreams themselves.
[2021 update: It's been more than 5 years since I wrote this post, so maybe there are more answers and clearer explanations out there. Or maybe I just missed them at the time. Let me know!]
References
Agargun, M. Y., & Cartwright, R. (2003). REM sleep, dream variables and suicidality in depressed patients. Psychiatry Research, 119 (1-2), 33-39
Beauchemin, K. M. & Hays, P. (1996). Dreaming away depression: The role of REM sleep and dreaming in affective disorders. Journal of Affective Disorders, 41 (2), 125-133
Cartwright, R., Luten, A., Young, M., Mercer, P., & Bears, M. (1998). Role of REM sleep and dream affect in overnight mood regulation: A study of normal volunteers. Psychiatry Research, 81 (1), 1-8
Cartwright, R., Baehr, E., Kirkby, J., Pandi-Perumal, S. R., & Kabat, J. (2003). REM sleep reduction, mood regulation and remission in untreated depression. Psychiatry Research, 121 (2), 159-167
Gais, S., Lucas, B., & Born, J. (2006). Sleep after learning aids memory recall. Learning & Memory, 13 (3), 259-262
Harvard Medical School (2008). Sleep and health. Retrieved [online] from http://healthysleep.med.harvard.edu/need-sleep/whats-in-it-for-you/health
Mallon, B. (2002). Dream time with children: Learning to dream, dreaming to learn. London: Jessica Kingsley Publishers
Maquet, P. (2001). The role of sleep in learning and memory. Science, 294 (5544), 1048-1052
Palagini, L & Rosenlicht, N. (2011). Sleep, dreaming, and mental health: A review of historical and neurobiological perspectives. Sleep Medicine Reviews, 15 (3), 179-186
Tribl, G. G., Wetter, T. C., & Schredl, M. (2013). Dreaming under antidepressants: A systematic review on evidence in depressive patients and health volunteers. Sleep Medicine Reviews, 17 (2), 133-142
Tyrrell, M. & Elliott, R. (2016). Depression and dreaming. Retrieved [online] from: http://www.clinical-depression.co.uk/depression-faq/depression-and-dreaming/
Vanderkerckhove, M., & Cluydts, R. (2010). The emotional brain and sleep: An intimate relationship. Sleep Medicine Review, 14 (4), 219-226
Walker, M. P. & Stickgold, R. (2004). Sleep-dependent learning and memory consolidation. Neuron, 44 (1), 121-133
Wilhelm, I., Rose, M., Imhof, K. I., Rasch. B., Büchel, C., & Born, J. (2013). The sleeping child outplays the adult's capacity to convert implicit into explicit knowledge. Nature Neuroscience, 16 (4), 391-393
Xie L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thiyagarajan, M., O'Donnell, J. Christensen, D. J., Nicholson, C., Iliff, J. J., Takano, T., Deane, R., & Nedergaard, M. (2013). Sleep drives metabolite clearance from the adult brain. Science, 342 (6156), 373-377
Zhang, Q. (2009). A computational account of dreaming: Learning and memory consolidation. Cognitive Systems Research, 10 (2), 91-101
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