Biochemical explanation of mental illness:
The monoamine hypothesis of depression:
● Group of neurotransmitters called the monoamines appear to be involved in
depression
○ Includes serotonin, dopamine, noradrenaline
● Depression involves lowered mood and disruption to activity
○ Believed that dopamine plays an important role in regulating our mood
○ Noradrenaline is particularly implicated in activity levels
○ Serotonin may be important in controlling the activity of noradrenaline
+ dopamine
● One version of the hypothesis says that reduction in serotonin levels, which
typically follows stressful events, leads to failure to regulate normal dopamine
& noradrenaline function
● Another version of the hypothesis says that disruption to monoamine levels is
the result of abnormally high levels of an enzyme that breaks down the
monoamines, reducing their action + disrupting the passage of information
around the brain
The dopamine hypothesis of schizophrenia:
● Dopamine is widely believed to be important in the functioning of several brain
systems that may be implicated in the symptoms of schizophrenia
● Early versions of the hypothesis identified a possible role for high levels of
dopamine in certain lower parts of the brain, can account for some symptoms
of schizophrenia
○ For example an excess of dopamine in those centres of the brain
responsible for speech production may result in hallucination of voices
● Recent take of hypothesis has focused instead on reduced dopamine levels or
activity in the brain’s cortex
○ Therefore low levels of dopamine in the prefrontal cortex, responsible
for thinking + decision making, may explain other symptoms of
schizophrenia such as apathy and incoherent thought/speech
Genetic explanations for mental illness
Genetic vulnerability to disease
● Researchers particularly interested in the serotonin transporter gene,
responsible for producing serotonin in the brain
● Gene comes in 3 forms; long-long, long-short, short-short
○ Believed that short form leads to insufficient serotonin production
The monoamine hypothesis of depression:
● Group of neurotransmitters called the monoamines appear to be involved in
depression
○ Includes serotonin, dopamine, noradrenaline
● Depression involves lowered mood and disruption to activity
○ Believed that dopamine plays an important role in regulating our mood
○ Noradrenaline is particularly implicated in activity levels
○ Serotonin may be important in controlling the activity of noradrenaline
+ dopamine
● One version of the hypothesis says that reduction in serotonin levels, which
typically follows stressful events, leads to failure to regulate normal dopamine
& noradrenaline function
● Another version of the hypothesis says that disruption to monoamine levels is
the result of abnormally high levels of an enzyme that breaks down the
monoamines, reducing their action + disrupting the passage of information
around the brain
The dopamine hypothesis of schizophrenia:
● Dopamine is widely believed to be important in the functioning of several brain
systems that may be implicated in the symptoms of schizophrenia
● Early versions of the hypothesis identified a possible role for high levels of
dopamine in certain lower parts of the brain, can account for some symptoms
of schizophrenia
○ For example an excess of dopamine in those centres of the brain
responsible for speech production may result in hallucination of voices
● Recent take of hypothesis has focused instead on reduced dopamine levels or
activity in the brain’s cortex
○ Therefore low levels of dopamine in the prefrontal cortex, responsible
for thinking + decision making, may explain other symptoms of
schizophrenia such as apathy and incoherent thought/speech
Genetic explanations for mental illness
Genetic vulnerability to disease
● Researchers particularly interested in the serotonin transporter gene,
responsible for producing serotonin in the brain
● Gene comes in 3 forms; long-long, long-short, short-short
○ Believed that short form leads to insufficient serotonin production
