Red Cross' clinical psychologist Rob Gordon on bushfires and mental health

And that means residents and firefighters will remain in a possibly dangerous heightened state of alert for an extended period.

Red Cross' clinical psychologist Rob Gordon said it was vital for people's long-term well-being that they take time to relax and escape 'adrenaline mode'

Dr Gordon said it was not healthy to remain in the 'heightened state of arousal' people go into to cope with emergencies, for a significant period of time.

"When you're in that mode you are properly attuned to fight a fire ... you're mentally prepared to deal with a physical threat," he said.

"Now the problem is when you're in that state you can't do long-term planning or prioritising or fill out complex forms.

"The longer people stay in that adrenaline mode the more they try to look at very simple, short-term immediate solutions, and they can't get them."

Dr Gordon said this results in feelings of anger and hopelessness and can stymie long-term recovery.

"You will totally put everything into the immediate rebuilding and recovery and you will do that at the expense of your relationships, your family life, your social networks and your health," he said.

"That's when two or three years down the track you'll find your marriage is in trouble, your health is deteriorating.... That's the second disaster. Those are irreversible losses."

Dr Gordon said right after a disaster, divorce, suicide and crime rates all decrease, but once the ashes settle they increase.

"Six months to two years down the track there's a time of real difficulty where everyone is stressed and depressed... you get an increase in divorce rates, suicide, crime etc and then in another year or so it evens out," he said.

Dr Gordon said there were four main groups of symptoms of PTSD - a continuing high state of arousal; reliving the trauma with intrusive thoughts; numbing and detachment; and the inability to function in family or work life.

He said PTSD could not be diagnosed until at least a month after a disaster because most people experience the symptoms short term.