Interactionist explanations

• A more modern approach

  The diathesis stress model - Although research shows the importance of biological factors in schizophrenia, it also highlights the significance of environmental factors.

  An explanation that links biological vulnerability to environmental stressors is the diathesis-stress model. This model explains that individuals will develop schizophrenia if they have a biological predisposition and if they are exposed to stressful situations
• Meehl’s (1962) original diathesis-stress model

  Diathesis (vulnerability) is entirely genetic – the result of a single schizogene, which led to a biologically based schizotypal personality – extremely sensitive to stress. 

  No amount of stress will lead to schizophrenia if the gene is not present. 

  However chronic stress in someone with the gene could lead to the development of the disorder – nature and nurture interact!
• Treatment according to interactionism

  As this model acknowledges an interaction of biological and psychological causes, it believes that a combination of  antipsychotic drugs and psychological therapies such as CBT should be employed

  Turkington et al. – we can still believe that schizophrenia has a biological basis but use CBT to relieve the psychological symptoms.
• Treatment according to interactionism

  UK – it is perfectly acceptable to use a combination of both therapies. 

  USA – conflict between biological and psychological therapies which has led to slower adoption of the interactionist model. Medication alone is more common here.
• Strengths

  • Strong support from the longitudinal study by Tienari. Additionally this is really strong because it had good controls and a blind interviewer. Valid Evidence. 
  • Practical applications – has educated us on the use of combined therapies for SZ – antipsychotics and CBT. 
• Strengths

  • The effectiveness of combination treatments has been shown in psychological trials. Tarrier et al (2004)  studied 315 patients. Patients who were in the combined therapy conditions showed lower symptom levels than those in control groups who only received drugs. 
  • Because of it’s interactionist approach it can be considered less reductionist than just the bio/psychological explanations alone. It takes into account more than one level of explanation (physiological/physical)
• ☹ Meehl’s original model is too simple. Notions of stress have evolved to include drug abuse and vulnerability has evolved to include childhood trauma. Stress and vulnerability can no longer be traced back to a single source. For example SZ is now known to be polygenic – caused by multiple genetic variations/factors.
• Weakness

  • It tells us there is an interaction between stress and vulnerability but not necessarily how they interact or work together. What mechanisms are at play? 
  • Just because combination treatments are better than biological or psychological alone doesn’t mean that the interactionist approach is definitely the cause of SZ. Just because a treatment method works doesn’t mean we have isolated the cause. Treatment-causation fallacy.