Research by the European College of Neuropsychopharmacology (ECNP) concluded that the behaviour patterns “precede many suicide attempts”.
The study said effective prevention measures were “urgently needed”.
The World Health Organisation estimates that there were more than 800,000 suicides worldwide in 2012.
The ECNP study evaluated 2,811 patients suffering from depression, of whom 628 had previously attempted suicide.
Researchers “looked especially at the characteristics and behaviours of those who had attempted suicide”, and found that “certain patterns recur” before attempts.
They said the risk of an attempt was “at least 50% higher” if a depressed patient displayed:
- “risky behaviour” such as reckless driving or promiscuous behaviour
- “psychomotor agitation” such as pacing around rooms or wringing their hands
- impulsivity – defined by the researchers as acting with “little or no forethought, reflection, or consideration of the consequences”
Dr Dina Popovic, one of the report’s authors, added: “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.”
He said she had two children and a successful career, and no one suspected she was at risk of suicide.
Speaking about the new research, he said: “We want to know more. We want somebody to correlate all this and make sense of what seems like a senseless situation.
“So I would welcome anybody who’s spent the time and bothered to assemble the pattern of behaviour because in Anna’s case there was a pattern of behaviour and I for one didn’t really spot it.”
Paul Farmer, of mental health charity Mind, said 6,000 UK people a year take their own lives – and “we don’t know enough about why that happens”.
He said the ENCP research had an “important message” about the “indicators that people should look out for” if they are worried about someone.
Factors already established included people being very withdrawn or very anxious, he said.
The study’s findings are being presented at the ENCP conference in Amsterdam on Sunday.