Numerous studies have shown how friendships can be good for our health.
The potential health benefits of romantic relationships are well documented.
A study reported by Medical News Today last year, for example, suggested that a spouse is 40-70% more likely to meet exercise recommendations if the other spouse does, while another study found that healthy lifestyle changes are more successful with partners.
But perhaps less well recognized are the wide-reaching health benefits of friendships, defined in simple terms as a mutual affection between two or more individuals.
It may not be surprising that friends are good for us, particularly when it comes to mental health; most of us have likely been through some bad times, during which friends were there to offer emotional support and help pull us through.
In fact, research has shown that people with a good support network are at significantly lower risk of depression, with one study reported by MNT last year revealing that in-person contact at least three times weekly almost halved seniors' risk of depression.
But the health benefits of friendships reach much further, as do the health risks associated with lack of companionship.
In this spotlight, we investigate the - perhaps surprising - ways in which friendship is good for us and take a look at why our pals play such an important role in health and well-being.
Your friends could be a stress-buster
Though quite possibly one of the most obvious benefits of friendship, a reduction in stress should not be overlooked.
According to The American Institute of Stress, around 3 in 4 doctors' visits are a result of stress-related illness, and stress is the basic cause of 60% of all human illness and disease.
However, a 2011 study published in the journal Developmental Psychology suggests that simply being around a good friend during a negative experience may reduce stress.
The study, which involved 103 children aged 10-12 years, found that children who spent time with a best friend throughout a negative experience had lower levels of the stress hormone cortisol in their saliva, compared with when negative experiences were endured with a parent, brother, sister, teacher or another individual.
And a new study from the University of California-Berkeley, recently published in the journal Neuropsychopharmacology, suggests that male friendships - often referred to as "bromances" - can reduce stress in bad situations.
To reach their findings, lead author Elizabeth Kirby, of the Department of Integrative Biology at UC-Berkeley, and colleagues housed male rats in the same cage.
Normally, male rats in this situation show aggression toward one another. However, the researchers found that subjecting the rodents to a moderate stressor - 3 hours of acute immobilization - actually caused them to bond.
Compared with the male rats that were housed together in an unstressed environment, those that were subject to the moderate stressor showed an increase in brain levels of oxytocin - known as the "love hormone" - and huddled more.
The team says this indicates that male friendships may alleviate the effects of stressful situations.
"A bromance can be a good thing," says Kirby. "Males are getting a bad rap when you look at animal models of social interactions, because they are assumed to be instinctively aggressive. But even rats can have a good cuddle - essentially a male-male bromance - to help recover from a bad day."
Better heart health for those with more friends
Heart disease is the leading cause of death for both men and women in the US, killing around 610,000 people in the country every year.
Frequent social interaction has been linked to better heart health.
High blood pressure is a key risk factor for heart disease and other cardiovascular conditions, including heart attack and stroke. But research has suggested that regular contact with friends could actually lower blood pressure.
A 2010 study published in the Journal of Circulation found that women who had frequent social interaction with a wide range of friends were more likely to have healthier blood pressure levels than their less social counterparts.
What is more, research has suggested that friendships can aid recovery from heart conditions.
A 2014 study published in the Journal of the American Heart Association, for example, found that patients who had experienced a heart attack were more likely to have depressive symptoms and poorer quality of life if they had low social support.
Good social networks could lower dementia risk
In the US, around 5.3 million people are living with Alzheimer's disease, of whom around 5.1 million are aged 65 and older. By 2025, the number of older adults with dementia is expected to rise to 7.1 million.
But could good social networks help stave off the illness? Some studies suggest so.
A 2008 study by researchers from Kaiser Permanente in Southern California, for example, found that women who maintained more friendships over a 4-year period were at 26% lower risk of dementia than those with smaller social networks, while those who saw friends and family daily halved their dementia risk.
Furthermore, a study presented at the Alzheimer's Association International Conference in Washington, DC, last year found that among individuals already diagnosed with dementia, loneliness was linked to 20% faster cognitive decline.
On the next page, we look at how friends could boost longevity, why friends may benefit health, and we offer tips on how to make friends.