Half of Australians report feeling lonely at least one day each week, with young adults, men, those living alone or with children more likely to report experiencing loneliness and social isolation.
Loneliness and social isolation have a similar risk factor for premature death as obesity, according to the Australia's Welfare 2019 report from the Australian Institute of Health and Welfare.
While loneliness has been linked to poor physical and mental health, as well as general dissatisfaction with life, social isolation has been linked to mental illness, emotional distress and poor health behaviours like smoking and physical inactivity.
The economic cost of loneliness hasn't been measured but "is likely to be substantial," the report said.
Most Australians will experience loneliness at some point, the report said, with one in three reporting experiencing an episode of loneliness between 2001 and 2009.
While most incidents of loneliness will last less than a year, for those with long-term feelings of loneliness, it is likely to last three years or more.
Studies have returned varying and contradictory results around whether someone's family situation, socio-economic factors or whether they lived regionally or in a city contributed to feelings of loneliness and isolation.
Unemployment and receiving income support were "substantial factors in the development of loneliness across age groups and gender," the report said, while also acknowledging another study showed men aged between 25 and 44 on high incomes were more likely to be lonely.
Living alone and not being in a relationship means someone is more likely to experience loneliness, with recently-separated men particularly vulnerable compared to both married men and recently-separated women.
Social media also had varying effects on people reporting loneliness, with some saying it helped them communicate with family and friends, but also having fewer online "friends" they consider real friends.
"Others have argued that online socialising can increase levels of loneliness as these relationships are generally fragile and shallow," the report said.
Pet owners were more likely to feel socially connected through owning a pet, which has been linked to more social contact.