Scientists will tell you we still don't understand enough about loneliness, and what this emotional state might do to people. But what we do know isn't good.

Mounting evidence suggests loneliness isn't just bad for your health, it's potentially far worse. While scientists are still figuring out the causes and connections, a new study reveals the phenomenon may be far more prevalent than we knew, and suggests loneliness peaks at key ages in people's lives.

Before now, research into which age groups are most susceptible to loneliness had demonstrated somewhat conflicting results.

Nonetheless, geriatric neuropsychiatrist Dilip Jeste from UC San Diego and his team hypothesised that older people might be more vulnerable to feelings of loneliness, on the basis that older people tend to spend more time alone.

But when they analysed psychological health assessments for 340 San Diego County residents aged between 27 and 101 years old, the results showed there was more going on.

As it happens, the hypothesis was at least partially borne out, with results suggesting loneliness severity peaked for people in their late 80s.

However, that wasn't the only spike in the data. Loneliness was also acute when people were in their late 20s, while another peak showed in the mid–50s.

The data can't tell us exactly why these peaks exist when they do, but the researchers speculate these spikes in lonely feelings are centred around the challenges and stresses that commonly coincide with these ages.

"The late 20s is often a period of major decision-making, which is often stressful because you often end up feeling that your peers made better decisions than you did, and there's a lot of guilt about why you did this or did that," Jeste explained to CNN.

By contrast, the "mid-50s is the midlife crisis period," Jeste said, complicated by middle age health challenges that can bring about a greater awareness of mortality.

Once people reach their late 80s, these kinds of psychological burdens can hit a new zenith (or rather a new low point, emotionally speaking), with increased physical frailty, conditions such as dementia, and the death of spouses and friends.

"It's probably the most understandable of the three periods," Jeste told CNN.

While the identification of these peaks in the data is remarkable, what most surprised the team was the prevalence of loneliness across all age groups.

According to the researchers, previously reported prevalence estimates in the US general population have ranged as high as 57 percent, but also as low as 17 percent.

Jeste and team suspected their own data would show something in the middle, but that's not what they found – discovering greater than three quarters (76 percent) of their cohort experienced moderate to high levels of loneliness, per the standardised scale they used to assess people.

"This is noteworthy because the participants in this study were not considered to be at high risk for moderate to severe loneliness," Jeste explains in a statement.

"They didn't have major physical disorders. Nor did they suffer from significant mental illnesses such as depression or schizophrenia… These participants were, generally speaking, regular people."

So far, so gloomy, you might well think, but the researchers did turn up one finding that should give cause for optimism.

In addition to gauging the participants' levels of loneliness and social isolation, the researchers also assessed them with the San Diego Wisdom Scale – a test co-developed by Jeste that measures wisdom according to a number of core domains tied to certain brain areas, and associated with people's capacity for things like prosocial attitudes, emotional regulation, reflection and self-understanding, and tolerance, among others.

Per the San Diego Wisdom Scale, the researchers found a strong inverse association between wisdom and loneliness. In other words, essentially, wise people experienced less loneliness.

"That may be due to the fact that behaviours which define wisdom, such as empathy, compassion, emotional regulation, [and] self-reflection, effectively counter or prevent serious loneliness," explains the first author of the study, Ellen Lee.

There's still a lot to learn about the complex psychological and physiological underpinnings of loneliness, and it's worth bearing in mind these new findings are based on an assessment of a relatively small group of people from one part of the world.

But in the face of something that's been identified as a global health epidemic, any insights that can help find a path to less loneliness have to be welcomed with open arms.

"We need to think about loneliness differently. It's not about social isolation," Jeste says.

"A person can be alone and not feel lonely, while a person can be in a crowd and feel alone. We need to find solutions and interventions that help connect people that help them to become wiser."

The findings are reported in International Psychogeriatrics.