Description of Mental Illness

Mental ill­ness can be described in a vari­ety of ways. The American Heritage Dictionary (4^th edit., 2000) describes it as: ​“Any of var­i­ous con­di­tions char­ac­ter­ized by impair­ment of an indi­vid­u­al’s nor­mal cog­ni­tive, emo­tion­al, or behav­ioral func­tion­ing, and caused by social, psy­cho­log­i­cal, bio­chem­i­cal, genet­ic, or oth­er fac­tors, such as infec­tion or head trau­ma. Also called emo­tion­al ill­ness, men­tal dis­ease, mental disorder.”

The National Alliance on Mental Illness describes men­tal ill­ness in the following way:

Mental ill­ness­es are med­ical con­di­tions that dis­rupt a per­son­’s think­ing, feel­ing, mood, abil­i­ty to relate to oth­ers and dai­ly func­tion­ing. Serious men­tal ill­ness­es include major depres­sion, schiz­o­phre­nia, bipo­lar dis­or­der, obses­sive com­pul­sive dis­or­der (OCD), pan­ic dis­or­der, post trau­mat­ic stress dis­or­der (PTSD) and bor­der­line personality disorder.

Intellectual Disability, for­mer­ly referred to as ​“men­tal retar­da­tion,” is defined dif­fer­ent­ly than mental illness. 

For more infor­ma­tion, vis­it DPIC’s page on Intellectual Disability.

Insanity or men­tal incom­pe­ten­cy is a severe form of men­tal ill­ness and is addressed sep­a­rate­ly by the legal sys­tem. Condemned pris­on­ers who do not under­stand what an exe­cu­tion is or lack a ratio­nal under­stand­ing of why the State wants to exe­cute them are exempt from exe­cu­tion. The Supreme Court first held in Ford v. Wainwright (477 U.S. 399 (1986)) that exe­cut­ing the insane is uncon­sti­tu­tion­al. It lat­er ruled in Panetti v. Quarterman (551 U. S. 930 (2007)) that a pris­on­er who under­stood the legal process can nev­er­the­less be incom­pe­tent to be exe­cut­ed if his men­tal ill­ness pre­vents him from ratio­nal­ly under­stand­ing why he is to be exe­cut­ed. The Court fur­ther clar­i­fied its incom­pe­ten­cy stan­dard in Madison v. Alabama (No. 17 – 7505 (2019)), rul­ing that a state can­not exe­cute a pris­on­er whose men­tal or med­ical con­di­tion pre­vents him from ratio­nal­ly under­stand­ing why he is to be exe­cut­ed, irre­spec­tive of what con­di­tion caused his impairment.

However, com­pe­ten­cy may fluc­tu­ate over time. If a pris­on­er’s men­tal com­pe­ten­cy has been restored, he or she can then be exe­cut­ed. Prisoners who are intel­lec­tu­al­ly dis­abled (for­mer­ly, ​“men­tal­ly retard­ed”) are exempt from the death penal­ty and can­not be exe­cut­ed. Prisoners who are men­tal­ly ill, but not incom­pe­tent to be exe­cut­ed, have no such exemption.