OCD Flashcards
Obsessions
Internal components of recurring intrusive thoughts or impulses that may be inappropriate
Compulsions
External component of repetitive behaviours or mental acts done to reduce anxiety caused by obsessions and feelings that something bad will happen if they don’t
Emotional characteristics of OCD
Anxiety - caused by obsessions and compulsions
Guilt and disgust - because aware their behaviour is excessive
Behavioural characteristics of OCD
Compulsions
Avoidance - of situations that will trigger their anxiety
Cognitive characteristics of OCD
Obsessions
Insight - know their obsessions and compulsions are irrational but can’t help it
Polygenic
Caused by many genes
How many genes may cause OCD (Taylor)?
Up to 230
How do genes lead to OCD?
They predispose the individual to OCD so if in right environment, it can develop
Aetiologically heterogenous
Origin of OCD has different causes and different groups of genes may cause OCD in different people, or cause different types of OCD
SERT gene
Serotonin transporter
What is the result of a mutated SERT gene in people with OCD?
Caused and increase in transporter proteins in the neuron’s membrane so there is an increase in reputase of serotonin into the neuron, decreasing levels of serotonin in the synapse
Serotonin
Happy hormone
COMT gene
Catechol-O-Methyl Transferase
Instructs an enzyme to break down neurotransmitters in the synapse
Dopamine
Reward hormone
connects feelings of pleasure to certain behaviours
effect of mutated COMT gene
causes decrease in COMT activity resulting in increased levels of dopamine
genetic explanation for OCD evaluation
relative environment of twin concordance is stressful
what is the “abnormal levels of neurotransmitters” explanation of OCD
low levels of serotonin mean mood-relevant information isn’t properly transmitted so mood and sometimes other mental processes are affected
what is the “abnormal brain circuits” explanation for OCD?
the caudate nucleus is damaged, so fails to supress minor worries from the OFC, and instead the thalami is alerted, which sends signals back to the OFC, acting as a worry circuit
Neural explanations of OCD evaluation
serotonin is a consequence of depressed associations and damage
OFC
Orbitofrontal cortex
where is the caudate nucleus?
in the basal ganglia
SSRI
selective serotonin reuptake inhibitor
what do SSRI’s do?
block the reuptake of serotonin in the brain so it remains active at the synapse where it continues to stimulate the post-synaptic neuron, reducing the symptoms of anxiety
what may be done if SSRIs are not effective after 3-4 months?
the dosage may be increased, it may be used in conjunction with CBT or a different antidepressant may be used
tricyclics action
block the transporter mechanism for both serotonin and noradrenaline into the presynaptic neuron after it has fired
what is the downside of tricyclics?
they generally have more side effects than SSRIs
Benzodiazepines
anti-anxiety drugs –> slow activity of CNS by enhancing activity of GABA
GABA action
locks onto receptor sites outside neuron
opens channel allowing chloride ions to flow into the neuron
make it harder for the neuron to be stimulated by other neurotransmitters
slows it’s activity and produces calming effect
Drug therapy for OCD evaluation
effective relapsing of cheap side effects working together
Who did the twin study that supports the genetic explanation of OCD
Nestadt
Nestadt figures
68% MZ concordance
31% DZ concordance
Lewis findings (OCD)
37% had parents with OCD and 21% had siblings with OCD
what is the low levels of neurotransmitter explanation for OCD based on?
The findings that OCD can be relieved by anti-depressants, especially those that increase levels of serotonin in the brain
Zohar et al. findings
drugs that increased levels of serotonin in OCD patients benefitted 60% of patientsc
challenge of Zohar et al. findings
most drug treatment studies have only found 50% improvement in OCD patients suggesting other factors involved.
what did MacGuire et al. find?
brain imaging studies indicate brain regions such as the OFC and caudate nucleus are associated with OCD
Soomro et al. findings
reviewed 17 studies in the use of SSRIs and found them to be more effective than placebos in reducing OCD symptoms up to 3 months after treatment, in the ST
what is the % range of OCD patients that get no benefit from SSRIs?
30-50%
relapse rates for OCD
90%