What is schizophrenia?

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Schizophrenia is a complex disorder influenced by several factors and characterised by a significant degree of variability in terms of both its causes and clinical presentation. It produces alterations in thought processes, perceptions, emotions and behaviour, and follows a progressive tendency.

Its origins are attributed to an early alteration in brain development due to various causes formed from a combination of genetic risk factors and environmental triggers. This interaction between genes and the environment induces cerebral toxicity in the dopamine system (a neurotransmitter found in several areas of the brain that is particularly important for the body’s motor function), and possibly in other neurotransmission systems, which causes severe anomalies in the connections between different areas of the brain.

It's very common?

Large epidemiological studies carried out by the World Health Organisation (WHO) indicate that schizophrenia affects 1% of the world’s population, regardless of sex, race or socio-economic level.

However, in light of new studies that have inspected these data further, we now know that the incidence of schizophrenia varies between populations over the course of time.

Its prevalence has decreased to 0.7% and it presents a greater tendency in men, populations in urban areas, cannabis consumers (marijuana or hashish) and immigrants.

The disorder usually appears in people aged 16–25 years and the average age of onset in men is almost four years earlier than in women. The typically later onset of schizophrenia in women partly explains why they have a better prognosis than men, because they have had more time to, for example, finish their studies, form a wide social network or start their own family before the appearance of the first episode.

The disease first appears before the age of 15 in approximately 5% of all people with schizophrenia. The condition tends to develop slowly when the onset is at a young age, while the predominant symptoms are social and emotional isolation (withdrawal), which are known as negative symptoms. This type of schizophrenia (early-onset) is more common in men and has a worse prognosis.

Types of schizophrenia

International classifications, including the World Health Organization’s latest version of the International Classification of Diseases (ICD-10), have traditionally subdivided schizophrenia into several different subtypes. The divisions were determined in function of the prevailing symptoms of each disease process. Thus, for example, if the patient presented predominantly positive symptoms, then they were diagnosed with paranoid schizophrenia.

However, these classifications into subtypes did not provide very useful categories with regards to making clinical decisions and therefore they do not feature in the latest version of the American Psychiatric Association’s Diagnostic and Statistical Manual (DSM-5). The next version of the ICD published by the WHO is also expected to abandon these subtypes.

Substantiated information by:

Miquel Bernardo
Miquel Bioque

Published: 20 February 2018
Updated: 20 February 2018

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