Five conditions – bipolar disorder, major depressive disorder, attention deficit hyperactivity disorder (ADHD), schizophrenia and autism – all share several generic risk factors, a major study has found.

The international study, published in The Lancet, compared the genetic codes of more than 33,000 people with a psychiatric disorder with some 28,000 people without one, and found that versions of four genes increased the odds of all five disorders.

The researchers hope the findings will help to move psychiatry away from describing symptoms to understanding what is happening in the brain to cause this.

Marjorie Wallace, chief executive of mental health charity SANE and the Prince of Wales International Centre for SANE Research, said the findings highlight the need to understand the genetic and biological factors of these life-changing conditions, in order that more effective treatments and therapies may be found.

“It could also erase some of the stigma surrounding them, much in the way that finding the causes of some cancers led to a change in public perception that cancers can be treatable and are not an umbrella term for fear,” she said.

“While there are no physical tests, the diagnosis of an illness such as schizophrenia depends on interpretation of symptoms alone, which can be open to misinterpretation and support unfounded theories of blame on such things as parental upbringing or an individual’s lifestyle.

“While it may take a decade for research studies like this to translate into new drugs and other treatments, we may yet be working towards a breakthrough which has so long eluded scientists working in this field.”

Carol Povey, director of the Centre for Autism at The National Autistic Society, said: “This research marks an important step in improving our understanding of autism and its complex causes. The study confirms that there is no single gene responsible for autism. It is thought to be the result of many different underlying physical and genetic factors.

“More research needs to be done before any concrete conclusions can be drawn about the causes and what this might mean for future developments, so it will be interesting to see how this research is built on to further enhance our knowledge of the condition.

“The most important thing is that we work to ensure people with autism receive the support they need to reach their full potential.”