Working out what is normal and what should be cause for concern in your infant or young child can be a tough call for parents and even some professionals, but the key is how frequent, sustained, intense and age-appropriate the behaviour.
Repeated tantrums, while natural in two-year-olds coming to terms with boundaries, might be an early warning sign of mental health problems in a five-year-old, according to experts.
"A lot of children who have difficulties will grow out of them, but there are also a lot of kids who don't," beyondblue's research, childhood and youth general manager Brian Graetz said.
"We are not very good at the moment in science to determine which kid is which but we have some good general rules.
"The longer the behaviour goes on for, the more stress it is causing to the kid and the parent and to the ones around them, the more it happens across multiple situations ... the more likely you are dealing with a bit of an issue that would be good to address."
And it was worth seeking professional help earlier rather than later if you had concerns, Dr Gaetz said.
For example, an aggressive child who did not have that aggression managed and did not learn more pro-social ways of interacting would find other children did not want to play with them and the relationship with their teachers more challenging.
While adults had the vocabulary to express how they were feeling and ask for help, babies and very young children did not have the same ability, so parents and professionals were left to work out signs and symptoms of mental distress from their behaviour.
Children with depression would appear clearly down, teary, distressed, withdrawn and with little interest in what was happening around them.
"They will have sleeping and eating issues, they don't want to play with friends. It is generally a change in behaviour that you notice," Dr Graetz said.
Alternatively, they might lash out, hitting or screaming at others or damaging property.
An anxious child reacted fearfully to strangers, had a limited ability to explore new situations, was overly vigilant about where their parent was and was clingy.
Steve Zubrick, head of population sciences at the Telethon Institute of Child Health Research, said it was hard to judge precisely the mental health of very young children, especially those under four years.
He said among infants and toddlers professionals looked for children who appeared safe and secure and who showed a good attachment to their caregivers.
"By the time we see a four and five-year-old we are expecting to see a little more regulation in their emotions, certainly a little more autonomy in their ability to explore and look around," he said.
"The types of emotional and behavioural problems that we are looking for in four and five-year-olds may concern things like withdrawal, problems with sleep, a child that is highly fearful or anxious and kids with major social problems … and then we have that other group which may show aggression."
The good news, according to child psychiatrist Caroline Goossens, from the Child and Adolescent Health Service, is that most difficulties respond quickly to intervention.
"Our main job is to optimise what is happening between the young child and their parent and to support that relationship in any way that we can and help it to thrive. Our aim is for parents to enjoy their relationship with their young children."
The first port of call for help could be a GP, child health nurse or parenting support organisation such as Ngala or Parenting WA.