110 Chapter 11
How else can we conceptualise two complex mood states (depression
and mania) that are normally mutually exclusive, but not always? Perhaps
it is like using a car’s brake and accelerator at the same time – not an
adaptive thing to do, not something we normally do, but not logically
impossible either. Or think about the way we spend our lives oscillating
from being awake to being asleep. There are intermediate drowsy states,
but we would not normally consider it possible to be fully awake and fully
asleep at the same time. However, this seems to be exactly what happens
in narcolepsy, a sleep disorder described in more detail in Chapter 20.
Symptoms such as sleep paralysis, cataplexy and hypnagogic hallucina-
tions reflect being completely awake while also being fully immersed in at
least some aspects of dreaming (REM) sleep. Mixed affective episodes may
reflect similar pathology in mood regulation, resulting in a combination of
mood symptoms that would not normally occur together.
From an evolutionary perspective, it is interesting to wonder about the
adaptive purpose of mood variation. When might it be adaptive to be
up or down? Perhaps mood variation is most likely to be adaptive when
it mirrors an individual’s position in the social hierarchy. Dominance in
the social hierarchy could justify a rather manic behavioural style that is
particularly energetic, pleasure-seeking, aggressive and sexually active. A
low or falling position in the hierarchy might equally justify a depressive
style that is more inhibited in all these respects. Think of the ‘big beasts’
or ‘alpha males’ of government or business. They radiate energy, power
and self-confidence, they make conquests, and they take big risks – a
set of potentially adaptive behaviours that can also add up to a manic
episode when things go wrong with the biology of mood control and these
behaviours occur in an inappropriate context.
Characteristic features
ICD-10 criteria for manic episodes are summarised in Box 11.2 – the
DSM-IV criteria are very similar. Hypomanic episodes are lesser versions
of manic episodes: whereas manic episodes result in severe interference
in personal functioning and generally last at least 7 days, hypomanic
episodes result in less interference and only need to be present for at least
4 days. Different sorts of episodes – manic, hypomanic, mixed and major
depressive episodes – are the building blocks from which bipolar disorders
are made. For example, DSM-IV distinguishes between:
Bipolar I disorderwhich refers to individuals who have experienced at
least one manic or mixed episode. There may be episodes of hypomania
and depression too.
Bipolar II disorderwhich refers to individuals who have experienced
at least one hypomanic episode and at least one depressive episode.
They have not experienced mixed or manic episodes (or they would
be classified as Bipolar I).