Two separate studies have linked schizophrenia to some specific gene variations moving closer to the causes and effective treatment of the devastating disease.

Schizophrenia is a severe mental disorder that affects around 1 percent of the general population, with 2 million men and women being diagnosed every year in the United States as having this disease. It is one of the most mysterious mental illnesses, since the brain of the affected patients is organically “intact,” unlike Alzheimer’s disease or Parkinson’s disease, where the brain shows distinctive signs of degradation (like the deposition of beta-amyloid protein that kills neurons and leads to dementia).

The disease is characterized by impairments in the perception or expression of reality, most commonly manifesting as auditory hallucinations, paranoid or bizarre delusions or disorganized speech and thinking. The disease is far more common in men than in women and is usually diagnosed in late adolescence or early adulthood. There is no cure, but symptoms can be improved with medication.

Scientists believe schizophrenia results from a combination of genetic predisposition and environmental influences. According to two studies published on the July 30 issue of the journal Nature, schizophrenia can be caused when genes are duplicated or deleted in an often random process that isn’t inherited from parents. However, family history remains a strong risk factor, 40 percent of patients having a close relative with the disease.

The two studies, conducted by Dr. Kari Stefansson of Decode Genetics in Iceland and the other by Dr. Pamela Sklar of the Massachusetts General Hospital, involved about 6,000 and 10,000 people from around the world, half of whom had schizophrenia. When making a thorough analysis of their genes, the researchers found one mutation on chromosome 1, two on chromosome 15 and confirmed a variant associated with the condition on chromosome 22.

The researchers said that people with schizophrenia are more than 10 times likely to have these rare chromosomal alterations compared to people who don’t have the illness.

“These findings give a great deal of hope – for individuals with schizophrenia and their families and loved ones and caregivers – that we’re moving towards an understanding of the causes of the disease,” Dr. Sklar said.

Moreover, the findings could be turned into a successful test to help in diagnosis, Dr. Stefansson said. Schizophrenia is currently diagnosed by its symptoms.

A separate study on the journal Nature Genetics conducted by Prof. Michael O’Donovan from the University of Cardiff Medical School revealed more common genetic variations held by many larger numbers of people but which offer a much smaller contribution to their risk of schizophrenia.

However, he concludes that it is still too early to tell how various genetic flaws might work together or separately to produce schizophrenia symptoms.

“It's very dangerous to say never, but to me, there are so many genes involved, that the idea of predicting whether someone will develop schizophrenia doesn't seem to me very likely,” he said.

The studies follow a finding in March by Mary-Claire King, professor of genome sciences at the University of Washington in Seattle and colleagues, published in the journal Science, according to which no one’s genes can be suspected for the presence of schizophrenia, but rather a large number of genetic glitches contribute to the onset of the illness.