Mood Disorders

Unipolar mood disorder

Only one extreme of mood is experienced

Bipolar mood disorder

Both depressed and elevated moods are experienced

Examples of unipolar mood disorder

E.g., only depression or only mania

Depression alone is much more common than

mania alone

Examples of bipolar mood disorder

E.g., some depressive episodes and some manic or hypomanic episodes

Worldwide lifetime prevalence of MDD:

16%

6% have experienced major depression in

the last year (2022)

Females are twice as likely to have

major depression

Bipolar disorders approximately equally affect

males and females

Women more likely to experience

rapid cycling

Women more likely to be in

depressive period

Occurs less often in

prepubertal children

In terms of prevalence, there’s a rapid rise in

adolescents

Adults over 65 have about

50% less prevalence than general population

Bipolar same in

childhood, adolescence, and adults

Prevalence of depression seems to be similar across

subcultures

3-month-olds can show

depressive symptoms

Young children typically don’t show

classic mania or bipolar symptoms

Mood disorder may be misdiagnosed as

ADHD

Children are being diagnosed with bipolar disorders at

increasingly high rates

Similar prevalence among U.S. subcultures, but

experience of symptoms may vary

Higher prevalence among Native Americans:

Four times the rate of the general population

Risk is higher if relative

has a mood disorder

Relatives of bipolar probands are more likely to

have unipolar depression

Concordance rates are high in

identical twins

Identical twins are two to three times more likely to

present with mood disorders than a fraternal twin of a depressed co-twin

Severe mood disorders have a

strong genetic contribution

Heritability rates are higher for

females compared to males

Some genetic factors confer risk for

both anxiety and depression

Serotonin regulates

norepinephrine and dopamine

Mood disorders are related to

low levels of serotonin

Permissive hypothesis:

Low serotonin “permits” other neurotransmitters to vary more widely, increasing vulnerability to depression

Stress hormones decrease neurogenesis in the hippocampus >

less able to make new neurons

What is the hallmark of most mood disorders?

sleep disturbance

Depressed patients have

quicker and more intense REM sleep

Sleep deprivation may temporarily

improve depressive symptoms in bipolar patients

Stress is strongly related to

mood disorders

Stress can lead to poor response to

treatment

Stress can lead to longer time before

remission

Gene-environment correlation:

People who are vulnerable to depression might be more likely to enter situations that will lead to stress

The learned helplessness theory of depression

Lack of perceived control over life events leads to decreased attempts to improve own situation

The learned helplessness theory of depression was first demonstrated

in research by Martin Seligman

Negative cognitive styles are

a risk factor for depression