Functional disorder

Functional disorders are a group of recognisable medical conditions which are due to changes to the functioning of the systems of the body rather than due to a disease affecting the structure of the body.^[1]

Functional disorders are common and complex phenomena that pose challenges to medical systems. Traditionally in western medicine, the body is thought of as consisting of different organ systems, but it is less well understood how the systems interconnect or communicate. Functional disorders can affect the interplay of several organ systems (for example gastrointestinal, respiratory, musculoskeletal or neurological) leading to multiple and variable symptoms. Less commonly there is a single prominent symptom or organ system affected.

Most symptoms that are caused by structural disease can also be caused by a functional disorder. Because of this, individuals often undergo many medical investigations before the diagnosis is clear. Though research is growing to support explanatory models of functional disorders, structural scans such as MRIs, or laboratory investigation such as blood tests do not usually explain the symptoms or the symptom burden. This difficulty in 'seeing' the processes underlying the symptoms of functional disorders has often resulted in these conditions being misunderstood and sometimes stigmatised within medicine and society.

Despite being associated with high disability, functional symptoms are not a threat to life, and are considered modifiable with appropriate treatment.^{[citation needed]}