Study links common antibiotic use to reduced schizophrenia risk

New Delhi, Nov 5 (PTI) Doxycycline, a common antibiotic, could help lower the risk of developing schizophrenia in young adults, a new study suggests.

The drug is prescribed for treating bacterial infections, including those of the respiratory tract and skin, and has been shown to reduce inflammation in brain cells in previous studies.

Schizophrenia is a mental disorder in which one harbours delusions and may have hallucinations. Symptoms can include an unpredictable behaviour or inappropriate emotional responses.

Researchers from institutes in the UK, Finland and Ireland analysed data from 56,400 adults born between 1987 and 1997 who availed psychiatric services during ages 13-18 and had consumed antibiotics. The analysis was based on information from the Finnish national health register.

Risk of schizophrenia after 10 years of follow-up was found to be 30-35 per cent lower among adults treated with doxycycline as an adolescent, compared to those treated with other antibiotics. The findings are published in the American Journal of Psychiatry.

Schizophrenia is considered a 'thought disorder', in which disorganised thought processes interfere with one's ability to interpret information and perceive reality.

The condition is estimated to affect one in every 200 people around the world, and in its acute state, can be the most impairing of all health conditions, according to the World Health Organization.

Lead researcher Ian Kelleher, professor of child and adolescent psychiatry at the UK's University of Edinburgh, explained synaptic pruning in the brain as a normal process in which connections are refined by shearing away links between specific brain cells.

"In schizophrenia, this pruning process seems to go into overdrive, resulting in too much pruning. Think of it like faulty electrical wiring: too many crucial connections are cut, disrupting communication between different brain regions," Kelleher said in an email to PTI.

Doxycycline, which can cross the blood-brain barrier and directly impact the central nervous system, has been shown to have anti-inflammatory effects and impact the brain's pruning process, the lead researcher said.

The team thus hypothesised that the antibiotic "could be a powerful candidate for preventing schizophrenia from developing in the first place".

Kelleher added that adolescence and early 20s are critical periods for brain development with a huge amount of synaptic pruning happening to make the brain efficient for the complex cognitive tasks of adulthood.

"We think it's probably quite important to intervene during this developmental window," he said, even as the team looks to figure out the ideal age for doxycycline treament.

Further, the study was an observational one, meaning no firm conclusions on cause-and-effect links could be drawn, he said.

Dr R. Mangala, joint director-residential services at Chennai's Schizophrenia Research Foundation (SCARF) and not involved with the study, said the link between doxycycline and schizophrenia is a fairly recently researched topic and there is no conclusive evidence yet.

She told PTI that the study is well-designed with a robust methodology and clearly identifies the right kind of population.

Dr Mangala added that the study looks at Finland's population registry, "which is among the best in the world. They have access to complete health data of people and so this is just possible for them to do that." The database presents an attractive opportunity for researchers to observe the antibiotic and schizophrenia link, she said.

Further, the 'target trial emulation' methodology employed in the study "will strengthen the causal inference, which is probably why the team chose it. They are trying to show there is a strong association between the use of doxycycline and a reduced risk of schizophrenia".

"Most tetracyclines (class of antibiotics) such as minocycline (treats respiratory and skin infection) have been considered to produce an action similar to doxycycline, especially because of their anti-inflammatory properties. This can help explain the theory of inflammation being a cause for psychosis," Dr Mangala said.

However, the protective effect is not so big that you can use it as an agent for treating the mental disorder, she said.

Other aspects of the study, including that it looked at medicines dispensed from a pharmacy and therefore may or may not have been consumed by an individual, are not definite, she added. PTI KRS KRS MG MG