Loners more likely mentally ill.
People persons more likely mentally ill.
We are naturally sociable creatures, chosing isolation is a possible indicator of some issue. Being in solitary confinment will make you unstable probably so isolating yourself is not good either. We need contact.
I'm a loner, and I'm positive I'm not mentally ill. If anything groups become mentally ill when they allow themselves to bend to the will of their patriarch/matriarch, which there is always one in every group. Kinda' like the average American bending to the will of the federal government because they've been taught to trust a likely untrustworthy government. Just look at the Obama Care scandal of "stupid" Americans just doing how the government do, or even the lack of protest about Obama's amnesty plan that people would rather ignore to b**** about Ferguson. But I'm off topic, essentially if people would just try to get to know a loner they may just be surprised at what they might learn from the experience.