While there is some overlap between biological psychiatry and neurology, the latter generally focuses on disorders where gross or visible pathology of the nervous system is apparent, such as epilepsy, cerebral palsy, encephalitis, neuritis, Parkinson's disease and multiple sclerosis. There is some overlap with neuropsychiatry, which typically deals with behavioural disturbance in the context of apparent brain disorder.
Biological psychiatry and other approaches to mental illness are not mutually exclusive, but may simply attempt to deal with the phenomena at different levels of explanation. Because of the focus on the biological function of the nervous system, however, biological psychiatry has been particularly important in developing and prescribing drug-based treatments for mental disorder.
In practice, however, psychiatrists may advocate both medication and psychological therapies when treating mental illness. The therapy is more likely to be conducted by clinical psychologists, psychotherapists, occupational therapists or other mental health workers who are more specialised and trained in non-drug approaches.
The history of the field extends back to the ancient Greek physician Hippocrates, but the term biological psychiatry was first used in peer-reviewed scientific literature in 1953. The term is more commonly used in the US than in some other countries such as the UK. The field, however, is not without its critics and the phrase "biological psychiatry" is sometimes used by those critics as a term of disparagement.
However, the biological psychiatrist typically does not discount psychoanalytic approaches (talk therapies). Medical psychiatric training generally includes both psychodynamic and biological approaches. Accordingly, psychiatrists are usually comfortable with a dual approach: "psychotherapeutic methods...are as indispensable as psychopharmacotherapy in a modern psychiatric clinic",
However in the late 1950s, the first modern antipsychotic and antidepressant drugs were developed: Chlorpromazine (also known as Thorazine), the first widely-used antipsychotic, was synthesized in 1950, and iproniazid, one of the first antidepressants, was first synthesized in 1957. In 1959 imipramine, the first tricyclic antidepressant, was developed.
Based significantly on clinical observations of the above drug results, in 1965 the seminal paper "The catecholamine hypothesis of affective disorders" was published. It articulated the "chemical imbalance" hypothesis of mental health disorders, especially depression. It formed much of the conceptual basis for the modern era in biological psychiatry.
Although the "chemical imbalance" hypothesis has been significantly revised since 1965, many newer medications (such as fluoxetine and other SSRIs) were developed based on the underlying theories of the hypothesis. More recent research points to deeper underlying biological mechansisms as the possible basis for several mental health disorders.
Modern brain imaging techniques allow noninvasive examination of neural function in patients with mental health disorders, however this is currently experimental. With some disorders it appears the proper imaging equipment can reliably detect certain neurobiological problems associated with a specific disorder. If further studies corroborate these experimental results, future diagnosis of certain mental health disorders could be expedited using such methods.
Another source of data indicating a significant biological aspect of some mental health disorders is twin studies. Identical twins have the same nuclear DNA, so carefully constructed studies may indicate the relative importance of environmental and genetic factors on the development of a particular mental health disorder.
The results from this research and the associated hypotheses form the basis for biological psychiatry and the treatment approaches in a clinical setting.
Since various biological factors can affect mood and behavior, psychiatrists often evaluate these before initiating further treatment. Such factors include hormone levels (especially thyroid), diet (especially alcohol and caffeine), and amount/quality of regular sleep and exercise.
Biological treatment of mental health disorders is not limited to drugs. Non-drug treatments include diet and exercise modifications, and in some severe cases treatments such as transcranial magnetic stimulation or electroconvulsive therapy may be indicated.
Nearly 100 years ago, Harvey Cushing, the father of neurosurgery, noted that pituitary gland problems often cause mental health disorders. He wondered whether the depression and anxiety he observed in patients with pituitary disorders were caused by hormonal abnormalities, the physical tumor itself, or both.
Another problem was the time lag between antidepressant biological action and therapeutic benefit. Studies showed the neurotransmitter changes occurred within hours, yet therapeutic benefit took weeks.
To explain these behaviors, more recent modifications of the monoamine theory describe a synaptic adaptation process which takes place over several weeks. Yet this alone does not appear to explain all of the therapeutic effects.
Recent research indicates a biological "final common pathway" may exist which both electroconvulsive therapy and most current antidepressant drugs have in common. These investigations show recurrent depression may be a neurodegenerative disorder, disrupting the structure and function of brain cells, destroying nerve cell connections, even killing certain brain cells, and precipitating a decline in overall cognitive function.
In this new biological psychiatry viewpoint, neuronal plasticity is a key element. Increasing evidence points to various mental health disorders as a neurophysiological problem which inhibits neuronal plasticity.
This is called the neurogenic hypothesis of depression. It promises to explain pharmacological antidepressant action, including the time lag from taking the drug to therapeutic onset, why downregulation (not just upregulation) of neurotransmitters can help depression, why stress often precipitates mood disorders, and why selective modulation of different neurotransmitters can help depression. It may also explain the neurobiological mechanism of other non-drug effects on mood, including exercise, diet and metabolism. Lastly, by identifying the neurobiological "final common pathway" into which most antidepressants funnel, it may allow rational design of new medications which target only that pathway. This could yield drugs which have fewer side effects, are more effective and have quicker therapeutic onset.
A vocal minority of patients, activists, and psychiatrists dispute biological psychiatry as a scientific concept or as having a proper empirical basis, for example arguing that there are no known biomarkers for recognised psychiatric conditions. This position has been represented in niche academic journals such as The Journal of Mind and Behavior and Ethical Human Psychology and Psychiatry, which publishes material specifically countering "the idea that emotional distress is due to an underlying organic disease." Alternative theories and models instead view mental disorder as non-biomedical and might explain it in terms of, for example, emotional reactions to negative life circumstances or to acute trauma.
Fields such as social psychiatry, clinical psychology, and sociology may offer non-biomedical accounts of mental distress and disorder for certain aliments and are sometimes critical of biopsychiatry. Social critics believe biopsychiatry fails to satisfy the scientific method because they believe there is no testable biological evidence of mental disorders. Thus, these critics view biological psychiatry as a pseudoscience attempting to portray psychiatry as a biological science.
R.D. Laing argued that attributing mental disorders to biophysical factors was often flawed due to the diagnostic procedure. The "complaint" is often made by a family member, not the patient, the "history" provided by someone other than patient, and the "examination" consists of observing strange, incomprehensible behavior. Ancillary tests (EEG, PET) are often done after diagnosis, when treatment has begun, which makes the tests non-blind and incurs possible confirmation bias.