Biological Explanation - OCD Flashcards
Genetic Explanations - Candidate Genes
1) Researchers have identified specific genes which create a vulnerability for OCD, called candidate genes.
- Serotonin genes, e.g. 5HT1-D beta, are implicated in the transmission of serotonin across synapses.
- Dopamine genes are also implicated in OCD and may regulate mood.
Both dopamine and serotonin are neurotransmitters.
Genetic - OCD is Polygenic
1) OCD is not caused by one single gene but several genes are involved.
2) One group of genes may cause OCD in one person but a different group of genes may cause the disorder in another person.
3) There is also evidence that different types of OCD may be the result of particular genetic variations, such as hoarding disorder and religious obsession.
Neural Explanations - Low Serotonin
1) Neurotransmitters are responsible for relaying info from one neuron to another.
E.g. if a person has low levels of serotonin then normal transmission of mood-relevant info does not take place and mood is affected.
Neural - Impaired Decision-Making
1) Some cases of OCD, and in particular hoarding disorder, seem to be associated with impaired decision-making.
2) This may be associated with abnormal functioning of the lateral frontal lobes of the brain (Frontal lobes are responsible for logical thinking and making decisions).
STRENGTH of Genetic Explanation
RESEARCH EVIDENCE
1) Researchers reviewed twin studies and found that 68% of identical twins (MZ) shared OCD as opposed to 31% of non-identical (DZ) twins.
2) Researchers found that a
person with a family
member with OCD is
around 4 times as
likely to develop it as
someone without.
—> This means that people who are genetically similar are more likely to share OCD, supporting a role for genetic vulnerability.
LIMITATION of Genetic Explanation
EXISTENCE OF ENVIRONMENTAL RISK FACTORS
1) Genetic variation
affects vulnerability
to OCD, but there are
also environmental risk
factors that trigger or
increase the risk of OCD.
2) Cromer et al. (2007)
found in one sample
over half of people
with OCD experienced
a traumatic event. OCD
severity correlated positively with number of traumas.
—> This means that
genetic vulnerability
only provides a partial
explanation for OCD.
EXTRA Evaluation of GE
ANIMAL STUDIES
1) Evidence from animal studies show particular genes are associated with repetitive behaviours in other species (e.g. mice, Ahmari 2016).
2) But the human mind is much more complex, so it may not be possible to generalise from animal repetitive behaviour to
human OCD.
—> This means that animal studies of candidate genes are probably not relevant to
understanding OCD.
STRENGTH of Neural Model
SUPPORTING EVIDENCE
1) Antidepressants that work on serotonin reduce OCD symptoms
This suggests that serotonin may be involved in OCD.
2) Also, OCD symptoms
form part of conditions
that are known to be
biological in origin e.g.
Parkinson’s disease
(Nestadt et al. 2010).
—> This means that
biological factors (e.g.
serotonin and processes
underlying Parkinson’s
disease) are likely to be
involved in OCD.
LIMITATION of Neural Model
NO UNIQUE NEURAL SYSTEM
1) Many people with
OCD also experience
depression. This
depression probably
involves disruption to
the action of serotonin.
2) It could simply be that
serotonin activity is
disrupted in many
people with OCD
because they are
depressed as well.
—> This means that serotonin may not be relevant to OCD symptoms.
EXTRA Evaluation of Neural
CORRELATION AND CAUSALITY
1) Some neural systems don’t work normally in people with OCD. The biological model suggests this is explained by brain
dysfunction causing the OCD.
2) However, this is just a correlation which does not necessarily indicate a causal relationship. OCD (or depression) might cause the abnormal brain function.
—> This means that there is a lack of strong evidence for a neural basis to OCD though correlations may eventually lead us to a cause.
