One strength of the biological approach is that it is a very scientific approach. The biological area often uses measurable and objective measures such as experiments and scanning techniques. For example, Sperry's study of split-brain patients can be considered to be highly scientific due to its experimental methods. These methods provide high internal validity and reliability.
One weakness of the biological approach is that it focuses too much on the 'nature' side of the nature/nurture debate. This can be considered reductionist as it argues that all behaviour is caused by hormones, neurotransmitters and genetics, when this is not the case. One theory is that schizophrenia is genetic, however, twin studies show that it is not completely genetic and the environment has a part to play.