Catatonic disorders are a group of symptoms characterized by disturbances in motor (muscular movement) behavior that may have either a psychological or a physiological basis. The best-known of these symptoms is immobility, which is a rigid positioning of the body held for a considerable length of time. Patients diagnosed with a catatonic disorder may maintain their body position for hours, days, weeks or even months at a time. Alternately, catatonic symptoms may look like agitated, purposeless movements that are seemingly unrelated to the person's environment.

Source : Encyclopedia of Mental Disorders

Catatonia was first medically described in the late 1800s. and has been intensively researched since then. It's usually* the result of acute psychiatric illnesses - typically Schizophreniaplugin-autotooltip__plain plugin-autotooltip_bigSchizophrenia

"Schizophrenia is a mental disorder characterized by abnormal social behavior and failure to understand what is real. Common symptoms include false beliefs, unclear or confused thinking, auditory and visual hallucinations, reduced social engagement and emotional expression, and a lack of motivation." and Major Depressive Disorderplugin-autotooltip__plain plugin-autotooltip_bigMajor Depressive Disorder

Major Depressive Disorder (MDD), also known simply as 'depression', is a mental disorder characterized by at least two weeks of pervasive low mood.

Current estimates are that severe depression affects around 2% of the global population at any given time, currently more than 150 million. The majority of cases don't appear to have an obvious personal and/or societal cause.. Its prevalence is estimated at around 10% of patients with acute psychiatric problems.

The pathophysiology that leads to catatonia is still poorly understood and a definite mechanism remains unknown. Neurologic studies have implicated several pathways, however, it remains unclear whether these findings are the cause or the consequence of the disorder.

Source : Wikipedia

* Note : It can also be triggered as a result of rapid drug/medication withdrawal.