Clinical psychologists need to have the ability to work with people whose problems differ in causation on a dimension ranging from presentations with mainly biological causation to those arising mainly from psychosocial factors.
Clinical psychologists should be able to apply knowledge of both biological and psychosocial factors pertinent to presentations, and know when such knowledge is pertinent. For example, biological factors are obviously crucial to understanding some conditions (e.g. learning disability, developmental delay, brain injury, dementia), whereas for others psychological or psychosocial determinants will be more critical (e.g. traumatic events resulting in depression /anxiety/ PTSD). In reality many presentations represent interactions between biological and psychosocial factors, making the ability to appraise each factor carefully an important skill when assessing, formulating and executing interventions.