CHAPTER 16: Schizophrenia and the Affective Disorders
Schizophrenia affects approx 1% of world's population. Has been around for 1000s of years.
“Schizophrenia” means “split mind”, but does not imply a split or multiple personality.
Eugen Bleuler coined the term: meant it to refer to a break w/ reality caused by disorganization
of various functions of the mind, such that thoughts/ feelings no longer work together normally.
Characterized by universal symptoms of disordered thoughts, delusions, hallucinations, and
often bizarre behaviors. There are 3 categories of schizophrenia symptoms:
1. positive symptoms: make themselves known by their presence. Includes hallucinations
(most commonly voices or olfactory), thought disorders (disorganized, irrational thinking),
and delusions (of persecution, grandeur, and control).
2. negative symptoms: known by absence of normal behaviors. Includes flattened emotional
response, poverty of speech, lack of initiative and persistence, anhedonia, social withdrawal.
3. cognitive symptoms: Includes difficult in sustaining attention, low psychomotor speed
(ability to rapidly/fluently perform movements of fingers, hands, legs), deficits in learning
and memory, poor abstract thinking, and poor problem solving.
Symptoms typically appear gradually over 3-5 yrs: 1
positive, then cognitive; positive yrs later.
Both adoption and twin studies indicate that schizophrenia is a heritable trait.
The incidence of schizophrenic children of 2 schizophrenic parents is less than 50% →
This means either several genes are involved or that having a “schizophrenia gene” imparts a
susceptibility to develop the disorder, the disease itself being triggered by other factors.
Test for susceptibility hypothesis: studies found that percentage of schizophrenic children was
identical for both the non- schizophrenic and the schizophrenic twin of a pair. This provides
evidence for heritability, and that carrying the “gene” does not necessarily lead to the disorder.
Another genetic factor is paternal age. Children of older fathers= more likely to develop
schizophrenia; this increased incidence is believed to be caused by mutations in spermatocytes
(cells that produce sperm); sperm divide
times, which increases room for DNA errors.
Candidates for “schizophrenia gene”: (no single one; a large # of rare mutations is suggested).
Mutations of DISC1 (
disrupted in schizophrenia 1
), a gene involved in regulation of
neuronal migration during development, have been found in families w/ high incidences of
Studies suggest that epigenetic mechanisms (which control expression of genes) may
contribute to development of schizophrenia as well as mutations.
Eg: long DNA strands that constitute chromosomes are wound around