Editing Temporomandibular joint dysfunction (section)

===Psychosocial factors===
[[Stress (psychological)|Emotional stress]] (anxiety, depression, anger) may increase pain by causing [[Autonomic nervous system|autonomic]], [[Viscus|visceral]] and skeletal activity and by reduced inhibition via the descending pathways of the [[limbic system]].<!-- <ref name="Aggarwal 2011" /> --> The interactions of these biological systems have been described as a vicious "anxiety-pain-tension" cycle which is thought to be frequently involved in TMD.<!-- <ref name="Aggarwal 2011" /> --> Put simply, stress and anxiety cause grinding of teeth and sustained muscular contraction in the face.<!-- <ref name="Aggarwal 2011" /> --> This produces pain which causes further anxiety which in turn causes prolonged muscular spasm at trigger points, [[vasoconstriction]], [[ischemia]] and release of pain mediators.<!-- <ref name="Aggarwal 2011" /> --> The pain discourages use of the masticatory system (a similar phenomenon in other chronic pain conditions is termed "fear avoidance" behavior), which leads to reduced muscle flexibility, tone, strength and endurance.<!-- <ref name="Aggarwal 2011" /> --> This manifests as limited mouth opening and a sensation that the teeth are not fitting properly.<ref name="Aggarwal 2011" />

Persons with TMD have a higher prevalence of psychological disorders than people without TMD.<ref name="Orlando 2007" /> People with TMD have been shown to have higher levels of anxiety, [[Depression (mood)|depression]], somatization and [[sleep deprivation]], and these could be considered important [[Risk factor (epidemiology)|risk factor]]s for the development of TMD.<ref name="Scully 2008" /><ref name="Orlando 2007" /> In the 6 months before the onset, 50–70% of people with TMD report experiencing stressful life events (e.g. involving work, money, health or relationship loss).<!-- <ref name="Scully 2008" /> --> It has been postulated that such events induce anxiety and cause increased jaw muscle activity.<!-- <ref name="Scully 2008" /> --> Muscular hyperactivity has also been shown in people with TMD whilst taking examinations or watching horror films.<ref name="Scully 2008" />

Others argue that a link between muscular hyperactivity and TMD has not been convincingly demonstrated, and that emotional distress may be more of a consequence of pain rather than a cause.<ref name="Glick 2003" />