New research has found three-year-olds are suffering from depression and anxiety, and there are claims smacking and yelling by parents is to blame.
A rise in mental illness in young people prompted the research – results showing parents who lash out at their kids are contributing to the problem.
The Murdoch Children's Research Institute study of 700 children has found stressed parents are lashing out at kids, fuelling abusive behaviour and setting them on a downward spiral.
The research revealed children who have tendencies to kick, hit and bite others, are usually the ones who were subjected to physical punishment from their parents at a young age.
The pressure stressed parents are putting on their children can have more serious outcomes later on, such as drug and alcohol abuse, unemployment, criminal activity and suicide.
Dr Jordana Bayer from the Murdoch Institute said smacking often related in behavioral problems for young children.
"We found that when toddler and pre-school children lived in families with lots of stress and yelling and smacking, they're more likely to develop behavioral and emotional problems by pre-school age," she said.
"I think that smacking's probably not the best way to manage behaviour."