Five disorders from depression to autism share a genetic link, which could pave way for new treatments Autism, ADHD, bipolar disorder, depression and schizophrenia overlap at a genetic level Two gene markers common to all of the disorders govern the balance of calcium in brain cells New understanding could help develop treatments The five most common mental health and developmental disorders share a common genetic root, a study has found. Scientists found a link between autism, attention deficit hyperactivity disorder (ADHD), bipolar disorder, depression and schizophrenia. The findings, from Massachusetts General Hospital in Boston, could revolutionise how doctors think about the conditions. Depression sufferers share certain gene mutations with those who have autism 'We have been able to discover specific genetic variants that seem to overlap among disorders that we think of as very clinically different,' study leader Dr Jordan Smoller told NBC News. The team found four genetic variants were associated with all five conditions. These markers were more common in people with the one of the disorders compared to healthy people. In particular, the research highlighted mutations in two genes that help govern the balance of calcium in brain cells. One of the roles calcium plays is in communication between cells. The discovery could lead scientists to reclassify the conditions and pave the way to new treatments, say the researchers writing in the The Lancet medical journal. Scientists scanned the genome, or genetic code, of more than 33,000 patients with mental disorders as well as 27,888 healthy individuals. The study was the largest investigation of genetic links to psychiatric illness ever conducted. While the five conditions have always been thought of as separate they do share some symptoms. For instance, mood and thinking problems can occur with schizophrenia, bipolar disorder and depression. And children with ADHD often have symptoms of other developmental disorders, such as autism. While the latest study doesn't prove every single case is related, it shows that they aren't totally separate at a genetic level. Dr Smoller added: 'Significant progress has been made in understanding the genetic risk factors underlying psychiatric disorders. Our results provide new evidence that may inform a move beyond descriptive syndromes in psychiatry and towards classification based on underlying causes. However, he pointed out that the variants they found were just a tiny fraction of the thousands of genes involved in the disorders. 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.