The biological approach to abnormality assumes that psychopathology is largely down to the four main physiological factors: infection, neuroanotmy, neurochemistry and genetics.

Infection is the result of pathogens entering the blood stream and entering the blood brain barrier or the nervous system. These pathogens cause diseases of the brain. For example in 1900's 3rd stage syphilis caused dementia and finally death. However this part of the biological approach is a very small explanation of abnormality, and with large advancements modern medicine is becoming decreasingly unseen. Another issue is multi-finality. For example schizophrenia has been associated with the flu during pregnancy, however not every expectant mother with flu has a schizophrenic child. A lot of other factors are involved in the disease, and simply labelling flu as the only cause is going to cause issues in the understanding of multiple factors.

Neuroanatomy refers to the different activities and structures of the brain regions and tissue. This is often tested through MRI scans of normal people and comparing to those mentally ill. One example is schizophrenia where the ventricles appear enlarged and the amount of grey matter in the brain is reduced. It is however hard to differentiate between causation and effect, as not knowing which proceeds which can only lead to guess work in terms of causation. Another issue is not every mentally ill person has the same structural abnormalities, and where one schizophrenic shows marked differences to a normal person, another schizophrenic can show little to none.

Neurochemistry refers to the function and availability of neurotransmitters such as dopamine, GABA, serotonin and noradrenalin. Dependent on the area of the brain they occur in, each affect behaviour in a different want. During synaptic response these neurotransmitters are passed across