WHO (World Health Organisation) highlighted the symptoms of this illness as follow.
Persistent delusions: this has to do with the individual having fixed beliefs that something is true, despite evidence to the contrary.
Experiences of influence, control or passivity: the experience that one’s feelings, impulses, actions, or thoughts are not generated by oneself, are being placed in one’s mind or withdrawn from one’s mind by others, or that one’s thoughts are being broadcast to others.
“negative symptoms” such as very limited speech, restricted experience and expression of emotions, inability to experience interest or pleasure, and social withdrawal; and/orextreme agitation or slowing of movements, maintenance of unusual posture
People with schizophrenia are said to often experience persistent difficulties with their thinking skills, such as memory, attention, and problem-solving.
Follow this link to learn more; https://www.who.int/news-room/fact-sheets/detail/schizophrenia
They were still using electric shock therapy in the 90s but to treat Major Depression and what was then called Manic Depression that did not respond to pharmaceuticals. My grandfather was subjected to it in the 60s (Major depression with paranoid delusions) and afterwards could not remember his last daughter being born.