Dr John Dearin, head professor at the University of Notre Dame's clinical school in Lithgow, has shared eight signs that someone might need some help.
The first, all-important step, Dr Dearin said, was to engage the person in a conversation.
Engage with them about their feelings, be a good listener, don't rush to provide advice that may not be wanted, offer to find some help and assure them that you care about them and that the relationship they have with you is really very important. Offer to talk to them at any time if they are feeling distressed, he said.
You should also recommend they seek professional help from a psychologist, doctor, counsellor or even a religious leader if they have an affiliation with a religious community.
1. Memory loss or a short attention span
If someone you know starts to experience frequent memory loss such as forgetting appointments this could be a sign of depression. Likewise, if they begin to have difficulty concentrating at work or school, thinking clearly or making decisions, it may be time for them to make an appointment with their local GP who may refer them to a psychologist.
2. Weight gain or loss
Most people are aware that weight loss and a loss in appetite could be one symptom of a mental health issue but its not well known that overeating and a lack of willingness to exercise could also be an early symptom of depression as people may seek comfort in food and lose motivation.
While everyone can be irritable at times, if someone is frequently or easily provoked, or perhaps you are noticing more conflict at home, it can be a sign of a deeper issue. Irritability can be a mark of anxiety, worry and distraction from issues troubling the person.
If you have a friend that starts to cancel plans with you in favour of staying in or they become less willing to participate in social activities, it may indicate that something is up mentally. Young people might become more secretive, spend more time on their phone or computer or try to avoid going to school.
It's worth making an extra effort to talk with any of your friends who exhibit this behaviour, as it could be a cry for help.
Anhedonia is when a person no longer finds enjoyment in activities that once gave a person pleasure. It is another common change in sufferers. In intimate relationships that could mean no longer seeming to enjoy time with a partner or loss of libido.
6. Conflict at work or school
A person generating conflict or being bullied in the workplace might be becoming depressed. Businesses should work towards providing mental health support to employees, especially with regard to stress.
7. Loss of productivity
If you are distracted mentally you are not going to be as productive at work or school. As an employer you might notice a decline in efficiency. In young people you might see a change in school grades.
People who are depressed or anxious can have trouble getting off to sleep because of preoccupation with issues that are causing their anxiety or depression. They wake up without feeling they've had a satisfying sleep, so they can developed disturbed sleep patterns.
Dr Dearin said it is critical that while the community engages in conversation about mental health they know what symptoms of a mental health issue might look like.
Unfortunately, many of the people who end up harming themselves fly under the radar, many of them are not even known to the mental health services, he said.
"That's why its so important to have a thumbnail sketch of the kind of symptoms that somebody might be presenting to alert their family and friends to the fact they are not well.
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