The challenge of the mind
Throughout the history of psychiatry, researchers have tried but failed to find any physical basis for the strikingly abnormal experiences and behaviours of patients with severe mental illness.
There are no blood tests or brain scans that can help us understand the nature of mental illness. Diagnoses are based on patterns in the clinical presentation, such as mood changes, delusions or ritualistic checking, and medications are prescribed on an empirical basis: we know that they work (sometimes with a surprising level of effectiveness), but we don’t really know why.
Mental illnesses are especially difficult to research because invasive investigations of the brain are not possible in the way they are for other organs. Even when physiological differences can be measured, it is often impossible to distinguish whether these are causes or effects of mental illness.