Schizophrenia is generally considered to be the most serious of all mental illnesses. It can exist alone or in combination with a mood disorder (i.e., schizoaffective disorder). It consists of two types of symptoms that are very different from one another. This has led to speculation that schizophrenia is not a single illness at all, but multiple co-occurring illnesses.
People with schizophrenia can have what are called "positive" and "negative" symptoms. Positive symptoms – hallucinations, delusions, and disorganized thinking – are easiest to see, and they're the ones most people are familiar with. But negative symptoms – lack of emotion, lack of motivation to start things, inability to experience pleasure, and limited speech – are what actually keep most people with schizophrenia from living independently, holding jobs, and managing everyday social situations.
Medications can help reduce some of the positive symptoms, but they don't have much effect on delusions and negative symptoms. Medications used to treat positive symptoms can sometimes make negative symptoms worse. Negative symptoms are challenging to treat, but social skills training and other activity-oriented interventions usually help.
Hallucinations – Auditory hallucinations (A/H) are by far the most common and cause the most problems. These are voices or sounds people hear that aren't really there. Sometimes the voices tell people to do things. These are called command hallucinations.
Delusions – Beliefs people hold with absolute certainty, even though they seem strange to other people and can easily be proven wrong. Delusions often become obsessions that preoccupy people's thoughts.
Disorganized thinking – Speech that doesn't communicate what the person intends, and behavior that doesn't make sense given what the person is trying to do. Disorganized thinking also makes it hard for people to follow directions and understand things other people are telling them.
Apathy – People with schizophrenia sometimes appear to have little or no interest in the world around them. They may even stop showering and changing clothes. Sometimes they cannot will themselves to start things. This is called "avolition". It makes holding a job or going to school very challenging.
Anhedonia – An inability to experience pleasure. People with schizophrenia have described this as a feeling of being hollow or empty regardless of what they do. It's one of the main reasons people with schizophrenia have difficulty forming close relationships. Combined with apathy, it results in people avoiding social situations and choosing to spend their time alone.
Flat or inappropriate affect – A person's facial expression can be unchanging and mask-like. Their voice may be monotonous. They make few gestures. Eye contact is often poor. When they do express an emotion, it may not match the situation. They may laugh at bad news or appear disappointed when receiving good news.
Reductions in speech – The technical term for this is "alogia" although it's usually referred to as "poverty of speech". People with alogia will answer questions with very brief responses. They may hardly speak at all. Their speech may be interrupted by long pauses. Or they may suddenly stop speaking in the middle of a sentence and be unable to recall what they were going to say. This is called "thought blocking". The ability to engage in casual conversation may be completely lost.
Impaired attention – Difficulty staying focused during conversations and an inability to concentrate even on simple tasks. Sometimes this is caused by A/H – voices that distract the person's attention – but the problem still exists even when people aren’t hearing voices.
Negative symptoms can be categorized in different ways. Some of the above categories could probably be combined. The main thing is just to be aware that negative symptoms exist. They often have a greater impact on people's lives than positive symptoms, but they're easily overlooked, or attributed to the person being overmedicated or depressed.