suggests that the onset of OCD is a result of our genetic makeup that we are born with
twin/family studies
Lewis (1936) found 37% had parents with OCD and 21% had siblings with OCD
Miguel et al (2005) used monozygotic (identical) twins and dizygotic (non-identical) twins. they found that 53%-87% chance of one MZ twin developing OCD if one already had it compared to a 22%-47% change in DZ - shows that OCD has a genetic basis but not a 100% concordance rate so other factors e.g environmental (impact)
COMT gene
this gene is involved in the production of the neurotransmitter dopamine. Take et al (2013) found one form of the COMT gene to be more common in OCD patients. This variation produced lower activity of the COMT gene and higher levels of dopamine
SERT gene
AKA: 5-HTT as it affects the transmission of serotonin leading to lower levels in the brain. Bengal et al (1999) compare 75 caucasian patients with OCD to 397 ethnically matched individuals who did not have OCD. it was found the patients with OCD were more likely (47%) to carry two copies of the long allele of the 5-HTT gene compared to controls (32%)
epigenetic
although we are born with our DNA that does not change, the way our cells and genes are activated in what can lead to changes in mental illness. these outside factors can affect the way the gene 'expresses' itself.
Neural explanations
Focus on what is happening in the brain
Neurotransmitters
Pass information (messages) from one neuron to another
Serotonin
Brain chemical that regulates mood, anxiety, memory and sleep
Dopamine
Brain chemical linked to experiencing motivation, rewards and compulsions
Increased dopamine leads to feelings of pleasure, but with OCD the anxiety associated with obsessive thinking is stopped only by the pleasure of completing the compulsion
Orbitofrontal cortex (OFC)
Sends signals to the thalamus about things that are worrying
If a part of the basal ganglia is damaged, the OFC signal is not stopped and the thalamus is alerted
OCD brain circuit
1. Impulse brought to attention
2. Behaviour performed to address impulse
3. Difficulty stopping/ignoring impulses from this circuit
PET scans show heightened activity in the OFC when OCD sufferers have active symptoms
strengths of the biological approach to explaining OCD
supportive research (nestadt et al, saxena and Rach)
practical application
nestadt et al
reviewed twin studies and found that 68% of identical twins shared OCD and 31% of non-identical twins
saxena and rach
reviewed studies of OCD that used PET,fMRI and MRI neuro imaging techniques and found consistent evidence of an association between the OFC and OCD symptoms
limitations of the biological approach to explaining OCD
relationship between biology and OCD is not clear cut
the research is correlational
lack of precision
reductionist
SSRIs
selective serotonin reuptake inhibitors
how do SSRIs work
the presynaptic cell sends information via a synapse
by sending this information, neurotransmitters are released into the gap
the receptors on the surface of the postsynaptic cell recognises these neurotransmitters and passes on the 'message'
90% of these neurotransmitters are released from the receiving receptors and taken up again by the sending cells
SSRIs to the reuptake of serotonin meaning it stays in the synapse for longer than it normally would
this can lead to repeated stimulation of the receptors on the post synaptic nerve ending and higher levels of serotonin
strengths of the biological approach for treating OCD
supportive research (soomro et al)
quick and easy to administer
soomro et al
reviewed studies comparing SSRIs to placebos and all 17 studies showed better results for SSRIs and that they are most effective when combined with a psychological treatment (e.g CBT)
limitations of the biological approach for treating OCD
issue of what happens when people stop taking the drug (Simpson et al)
side effects to drugs (indigestion, blurred vision, weight gain)
simpson et al
suggests that 45% of patients treated with medication relapsed within 12 weeks compared to 12% who had received a psychological treatment