AQA Psychology: The biological approach - treating OCD; drug therapy. How do they work?

12th February 2016 at 15:02

Subject Genius, Nick and Bethan Redshaw, The biological approach to treating OCD

  • Essential for understanding why drug therapy is effective biological treatment for OCD
  • The confusion in scientific reports, books especially older books even biology books on how SSRI and Tricyclic's work is clarified here.

The biological approach assumes that behaviour can be explained through chemical imbalances and the role of hormones.  You will recall from the Approaches section that the complex network of the PNS, that consists of millions of neurons that carry information to and from the central nervous system is sub divided into the ANS and the SNS, which controls muscle movement and its primary role is to connect the CNS to the senses, organs, muscle and skin.  Disruption in the SNS leading to chemical imbalances would logically lead to the observable behavioural characteristics of OCD. 

In fact, research has shown that OCD patients only respond effectively to drugs that regulate the neurotransmitter serotonin.  This suggests a strong link between OCD and low levels of serotonin. Extensive research has been carried out since the 1960’s and all have found a critical link between low levels of serotonin and OCD.  In clinical studies carried patients were given drugs that increase levels of serotonin in the brain, such as the SSRI anti-depressant and in all cases the symptoms and behaviour of OCD decreased (Murphy and Piggott 1990, Goodman et al 1995).

So how do they work, basically they stop the uptake of the neurotransmitters serotonin during synaptic transmission.  The confusion in reports, books especially older books even biology books is the use of the term high levels of neurotransmitters in the case of mental illness it is actually the fact that the neurotransmitter is crossing the synaptic junction to fast and causing to high an excitation at the adjoining neurone causing to great an electric impulse resulting in the observable behaviour link to OCD.

Subject Genius, Nick and Bethan Redshaw, The biological approach to treating OCD

So SSRI,s and tricyclic drugs reduce the uptake and slow the transmission, reducing the excitation and lowering the electric impulse bringing the observable behaviour to a more normal level. However, the brain instructs the body to carry on releasing the neurotransmitters so increasing the levels in the brain BUT the message cannot reach its destination.

This biology may be complicated, so Simply imagine an airport with 4 runways three are closed due to an emergency planes still arrive but are held in a holding pattern and slowly land.  Levels of passengers getting off is less so passport control is not so busy, but the holding pattern gets busier and busier (in biological terms serotonin levels increase in the brain).


Please see Nick and Bethan's resources on this topic:


Nick & Bethan Redshaw are authors of the highly successful Independent Learner Series for AQA Psychology Specification.