Children are the hidden victims of family violence, which places them at significant risk of mental health problems, an Australian study has found.

The report by Australia's National Research Organisation for Women's Safety has found children exposed to domestic and family violence (DFV) are five times more likely to need mental health assistance by the age of 18 than their peers.

Researchers used police and health records to assess the impact on children born in Western Australia between 1987 and 2010.

Their experiences were typically visible in police or hospital data by age six. But on average, children only received a mental health response six years later at age 12.

Children who experienced DFV were twice as likely to develop a substance use disorder and more likely to be diagnosed with anxiety and depression.

Lead author and UWA research fellow Carol Orr said exposure to DFV was one of the most common and harmful traumatic childhood events.

"Children experiencing domestic and family violence have a 36 per cent greater risk of depression, a 49 per cent greater risk of anxiety, and an almost 60 per cent greater risk of intentional self-harm," Dr Orr said on Tuesday.

"Children need to be recognised as victims in their own right."

Researchers believe experiencing DFV creates an ongoing stress response in a child's brain, increasing their risk of physical and mental illness.

Some children may initially seem unaffected by trauma, but struggle with their mental health years later.

UWA professor Colleen Fisher said early intervention was key to helping children avoid future mental health difficulties.

"Children are sometimes described as the hidden victims of family and domestic violence, and these findings show there's an urgent need for early and appropriate intervention to help children and mitigate any harm," she said.