A new study has shown that people under depression who display signs of agitation and impulsive behavior are at least 50 per cent more likely to attempt suicide, Science daily reports.

For the study, researchers evaluated 2,811 patients who were suffering from depression. Out of the 2,811 patients, 628 had already attempted suicide. Each of the patients were interviewed separately by a psychiatrist.

"We found that 'depressive mixed states' often preceded suicide attempts. A depressive mixed state is where a patient is depressed, but also has symptoms of 'excitation,' or mania," said Dina Popovic, from the Hospital Clinic de Barcelona in Spain. 

"In fact 40 per cent of all the depressed patients who attempted suicide had a "mixed episode" rather than just depression," said Popovic. 

"All the patients who suffer from mixed depression are at much higher risk of suicide," said Popovic. 

The study found that certain behavior patterns recur before suicide attempts. The study looked at behaviors of those who had attempted suicide compared these to depressed patients who had not attempted suicide. 

"We also found that the standard DSM criteria identified 12 per cent of patients at showing mixed states, whereas our methods showed 40 per cent of at-risk patients," said Popovic. 

"This means that the standard methods are missing a lot of patients at risk of suicide," said Popovic. 

The study may help in the care of patients affected with depression, as it shows the clinical factors which confer major risk of suicide attempts, researchers said. 

"This is an important message for all clinicians, from the GPs who see depressed patients and may not pay enough attention to these symptoms, which are not always reported spontaneously by the patients, through to secondary and tertiary level clinicians," said Popovic.