What is Schizophrenia?
Schizophrenia is a brain disorder characterized by core positive symptoms (delusions, hallucinations, disorganization) and negative symptoms (reduced emotional expression and avolition) lasting for at least six months. Schizophrenia usually begins in the second and third decade of life. After the first episode, recovery is common but the majority of patients experience further episodes with partial remission in between. Schizophrenia has a strong genetic component but non-genetic factors (illicit drug abuse, urbanicity, migration, advanced paternal age and obstetric complications) make a significant contribution. Antipsychotic medication is the most effective intervention for symptom control and relapse prevention. Psychoeducation, psychological and vocational interventions are important adjunctive components of care.
What are schizophrenia spectrum disorders?
These are disorders that present with symptoms similar to schizophrenia but these symptoms are either more limited or relatively short-lived. The most recent classification of mental disorders by the American Psychiatric Association recognizes the following conditions as part of the schizophrenia spectrum:
- Delusional disorder: Symptoms are limited to delusions and typically there are no other psychotic or negative symptoms
- Brief psychotic disorder: Symptoms last more than one day but less than one month.
- Schizophreniform disorder: Symptoms last more than one month but less than six months.
- Schizoaffective disorder: Psychotic and severe mood symptoms occur together but are preceded or followed by at least two weeks of delusions or hallucinations without prominent mood symptoms.
- Schizotypal personality disorder: Symptoms do not typically reach full psychosis but are more pervasive across the lifespan.
Psychotic symptoms may be present in many different conditions other than schizophrenia and spectrum disorders. It is therefore important exclude other medical illness (e.g. brain tumor) that can cause psychosis by their direct effect on the brain. The same applies for psychotic symptoms arising in the context of substance/medication-induced psychotic disorder where symptoms are attributed to the direct effects of illicit drugs, prescribed medications or environmental toxins (e.g. lead).
Symptoms of Schizophrenia
Positive psychotic symptoms represent experiences and behaviors that healthy people rarely have (i.e. they are abnormal by their presence in patients). These are:
- Delusions: These are fixed beliefs that are not amenable to change even when contradicted by facts. The most common are persecutory delusions. People with persecutory delusions believe (in the absence of any objective evidence) that other people or organizations intend to persecute them or harm them.
- Hallucinations: These are vivid and clear experiences that that occur without anything external causing them and can involve any of or five senses (sight, hearing, taste, smell and touch). The most common are auditory hallucinations. People with auditory hallucinations hear sounds or voices that do not exist.
- Disorganized thinking (speech): Individuals with this symptom seem unable to follow their train of thought. Their answers are often unrelated to the questions or they may drift from one topic to another. When severe, patients’ speech can be difficult to follow and may even be incoherent.
- Disorganized or abnormal behavior: When this symptom is present, individuals seem unable to perform their daily activities in an ordered manner. When severe, it can manifest as agitation or even catatonia. In the case of catatonia, individuals seem unresponsive to their environment and can either remain mute and motionless for long periods or alternatively they move about a lot without engaging in any meaningful activity.
Negative symptoms refer to mental functions and abilities that are present in healthy people but are diminished or lost in schizophrenia (i.e. abnormal by their absence in patients). These are:
- Diminished emotional expression: Patients usually have reduced eye contact and facial expression of emotions as well as reduced expressive speech, hand gestures and body movements.
- Avolition: Patients find it difficult to motivate themselves in starting activities or in participating in ongoing activities around them.
Apart from these core clinical symptoms patients may experience periods of depression. Patients also often have cognitive difficulties which manifest as difficulties with attention and memory.
Causes of Schizophrenia
It is generally agreed that schizophrenia is caused by several genetic and non-genetic risk factors.
Genetic factors: It has long been known that the risk for schizophrenia is increased in the blood relatives of patients. The risk increases with genetic proximity to an individual with the diagnosis. Monozygotic (i.e. identical) twins are genetically very similar and therefore they have the highest risk. The risk is lower in siblings, half-siblings, offspring and second degree relatives (cousins, uncles and aunts) than it is in monozygotic twins but remains higher than that of the general population.
More recent studies involving many thousands of individuals have helped to discover more than 60 individual genes that can increase the risk for schizophrenia. However, none of these genes can cause schizophrenia on its own. Further studies are now underway aiming to identify additional genes and map biological pathways from genes to clinical symptoms.
Alterations in brain chemistry: Neurons are the main cells that make up the brain. They communicate with each other by releasing chemicals called neurotransmitters. Two of the most important neurotransmitters are dopamine and glutamate. In healthy people, the release of dopamine and glutamate is very finely balanced. This fine balance is disturbed in schizophrenia with excessive dopamine release being a key feature of acute psychotic symptoms.
Alterations in brain structure and function: Neurons are connected in a precise way. This is an important feature of normal brain structure as it allows coordinated collaboration between brain regions that is essential for normal brain function. In schizophrenia, the “wiring” of the brain is sub-optimal giving rise to reductions in the volume of key regions and interferes with coordinated activation between brain regions. These changes are not visible with the naked eye but require detailed analyses of patients’ brain scans.
Illicit drug abuse: Frequent cannabis use in early adolescence carries an increased risk for subsequent development of schizophrenia. This is particularly important for individuals that have other risk factors for the disorder. Moreover, cannabis use differs from other risk factors because it is not fixed. For example, an individual may not be able to change their genetic inheritance but they can choose whether to use drugs or not.
Additional factors that increase the risk of schizophrenia are living in big cities (urbanicity), migration, childhood abuse, pregnancy and birth complications, and advanced paternal age.