Disorders of diminished motivation

Disorders of diminished motivation (DDM) are a group of disorders involving diminished motivation and associated emotions. Many different terms have been used to refer to diminished motivation. Often however, a spectrum is defined encompassing apathy, abulia, and akinetic mutism, with apathy the least severe and akinetic mutism the most extreme.

DDM can be caused by psychiatric disorders like depression and schizophrenia, brain injuries, strokes, and neurodegenerative diseases. Damage to the anterior cingulate cortex and to the striatum, which includes the nucleus accumbens and caudate nucleus and is part of the mesolimbic dopamine reward pathway, have been especially associated with DDM. Diminished motivation can also be induced by certain drugs, including antidopaminergic agents like antipsychotics, selective serotonin reuptake inhibitors (SSRIs), and cannabis, among others.

DDM can be treated with dopaminergic and other activating medications, such as dopamine reuptake inhibitors, dopamine releasing agents, and dopamine receptor agonists, among others. These kinds of drugs have also been used by healthy people to improve motivation. A limitation of some medications used to increase motivation is development of tolerance to their effects.

Disorders of diminished motivation (DDM) is an umbrella term referring to a group of psychiatric and neurological disorders involving diminished capacity for motivation, will, and affect.

A multitude of terms have been used to refer to DDM of varying severities and varieties, including apathy, abulia, akinetic mutism, athymhormia, avolition, amotivation, anhedonia, psychomotor retardation, affective flattening, akrasia, and psychic akinesia (auto-activation deficit or loss of psychic self-activation), among others. Other constructs, like fatigue, lethargy, and anergia, also overlap with the concept of DDM. Alogia (poverty of speech) and asociality (lack of social interest) are associated with DDM as well.

Often however, a spectrum of DDM is defined encompassing apathy, abulia, and akinetic mutism, with apathy being the mildest form and akinetic mutism being the most severe or extreme form. Akinetic mutism involves alertness but absence of movement and speech due to profound lack of will. People with the condition are indifferent even to biologically relevant stimuli such as pain, hunger, and thirst.

Less extreme forms of DDM, for instance apathy or anhedonia, can be a symptom of psychiatric disorders and related conditions, like depression, schizophrenia, or drug withdrawal. More extreme forms of DDM, for instance severe apathy, abulia, or akinetic mutism, can be a result of traumatic brain injury (TBI), stroke, or neurodegenerative diseases like dementia or Parkinson's disease.

Reduction in motivation and affect can also be induced by certain drugs, such as dopamine receptor antagonists including D₂ receptor receptor antagonists like antipsychotics (e.g., haloperidol) and metoclopramide and D₁ receptor antagonists like ecopipam, dopamine-depleting agents like tetrabenazine and reserpine, dopaminergic neurotoxins like 6-hydroxydopamine (6-OHDA) and methamphetamine, serotonergic antidepressants like the selective serotonin reuptake inhibitors (SSRIs) and MAO-A-inhibiting monoamine oxidase inhibitors (MAOIs), and cannabis or cannabinoids (CB₁ receptor agonists).