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Sleep and depression

raisin asleepSleep disturbance is a key symptom of depression – difficulty in falling asleep at night and/or waking up too early in the morning is very common. The importance of sleep was discussed in a previous post; this one looks at the role of dreaming. But first, some background. Studies show that the sleep architecture – patterns of sleep throughout the night (see below) – in depressed people is different:

Compared with normal controls, sleep continuity of depressed subjects is often impaired, with increased wakefulness (more frequent, and longer periods of wakefulness), and reduced sleep efficiency. Sleep onset latency is significantly increased and total sleep time reduced. Rapid eye movement (REM) latency is often shortened, and the duration of the first REM period is increased. The number of eye movements in REM is also increased.

The total amount of slow wave sleep is often decreased in depression, compared with normal controls…   Also the normal pattern of slow wave activity in the brain decreasing from the first to the last NREM episode is disrupted. (Nutt, 2008)

 

Sleep ‘architecture’ (source: wikipedia)

  • non REM (NREM) stage 1: This is a stage of sleep that usually occurs between sleep and wakefulness, and sometimes occurs between periods of deeper sleep and periods of REM. The muscles are active, and the eyes roll slowly, opening and closing moderately.
  • NREM stage 2: In this stage, sleepers become gradually harder to awaken.
  • NREM stage 3: Formerly divided into stages 3 and 4, this stage is called slow-wave sleep. The sleeper is less responsive to the environment; many environmental stimuli no longer produce any reactions.
  • REM: The sleeper now enters rapid eye movement (REM) where most muscles are paralysed. REM sleep is turned on by acetylcholine secretion and is inhibited by neurons that secrete serotonin.

605px-Sleep_Hypnogram.svgAn adult [normally] reaches REM approximately every 90 minutes, with the latter half of sleep being more dominated by this stage. REM sleep occurs as a person returns to stage 1 from a deep sleep. The function of REM sleep is uncertain but a lack of it impairs the ability to learn complex tasks.

Sleep proceeds in cycles of REM and NREM, usually four or five of them per night, the order normally being N1 → N2 → N3 → N2 → REM. There is a greater amount of deep sleep (stage N3) earlier in the night, while the proportion of REM sleep increases in the two cycles just before natural awakening.

 

The role of dreaming

Dreaming probably occurs throughout the sleep cycle but is mostly associated with REM sleep. There isn’t scientific consensus on the role of dreams but one plausible proposal with relevance to depression is that dreams help regulate mood.  Emotionally charged events that happen during the day are woven into dreams at night that incorporate memories of similar events and emotions, allowing the brain to compare past events and their impact with the new one, and to file the memory.  Sort of mental digestion, processing emotions while we sleep.

When some disturbing waking experience is reactivated in sleep and carried forward into REM, where it is matched by similarity in feeling to earlier memories, a network of older associations is stimulated and is displayed as a sequence of compound images that we experience as dreams.

This melding of new and old memory fragments modifies the network of emotional self-defining memories, and thus updates the organisational picture we hold of “who I am and what is good for me and what is not.”

In this way, dreaming diffuses the emotional charge of the event and so prepares the sleeper to wake ready to see things in a more positive light, to make a fresh start. This does not always happen over a single night…..[it] may take many nights. (Cartwright, 2010)

 

Dreaming and depression

Cartwright’s research with depressed people going through divorce found that those who dreamt about their ex-spouse – angry, emotional dreams – generally recovered from their depression. Those who were passive and unemotional in their dreams did not fare so well, leading her to suggest that ‘dream collection might become a screening tool useful in determining a patient’s psychological resiliency’.

Dreams also show a progression through the night: whilst negative dreams occurring early in the night may reflect a within-sleep mood regulation process taking place, those that occur later may indicate a failure in the completion of this process (Cartwright, 1998)

The University of Hertfordshire has taken this mood-regulation idea a step further by exploring whether the emotional nature of dreams can be influenced, and whether this in turn affects waking mood. The Dream:On smartphone app has been developed so you can try it for yourself (not available on android, sadly).

The final dream of the night influences people’s morning mood, and so making that dream more positive may well help thousands face the day with a smile on their face.

In addition, sleep scientists have long known that the dreams of those diagnosed with depression are especially long, frequent, and negative. It’s possible that dream influence will become a radically new therapeutic tool in the fight against depression. It’s early days, but we’re very excited about the potential power of dream control.  (Wiseman, Dream:On)

 

So what?

There is a lot to think about here. I will reflect on these in particular:

  • does more sleep mean more dreaming, and therefore more emotional processing?
  • might be worth doing a dream diary for a while, noting any association between dreams and mood
  • might be worth trying to replicate the Dream:On idea of influencing the pre-wake dream
  • how much I love this song…

 

References/further reading

Rosalind Cartwright (2010) The Twenty-four Hour Mind Oxford University Press

Rosalind Cartwright (1998) Role of REM sleep and dream variables in the prediction of remission from depression

David Nutt (2008) Sleep disorders as core symptoms of depression

 

 

depression and dreaming: when mental digestion leaves a bad taste in the mood

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