The subject of mental health is a wide and varied one, full of misinterpretation and thus, misunderstanding. 
The subject is undoubtedly sensitive.

On this page I am in no way claiming to be an expert on all mental health issues, their effects and causes. I am however going to share with you what I understand to be an important consideration for anyone who already communicates with those in spirit, or who is considering doing so. 

So, is there a possible link between people who have an interest in all things paranormal and the likelihood of that person at some point experiencing mental health issues?

If there is, the over-riding question is one of the 'chicken and egg' type. So in other words, "which came first?"

One theory is that someone who has a tendency towards experiencing problems with their mental health, will inevitably look towards seeking answers to the meaning of life. To look for proof of something more, and so in theory, are more likely to delve into the field of the paranormal. Of course belief in this theory will depend entirely on whether you buy into the idea that people CAN have a tendency towards conditions like Depression and Bi-Polar, or whether you believe these conditions are infact born more out of life experience. 

Maybe you are more likely to believe that once we begin delving into the unknown, gaining knowledge of the spirit world and opening ourselves up to external influences that we are inevitably making ourselves vulnerable to mental health issues later on as we begin to question our mortality for example. 

Whichever camp you sit in on this, even if you sit in neither, the ability certain spirits have to influence our minds and emotions cannot be ignored.
It is well documented that some people who have practised divination of some kind, have them gone on to experience strong emotions, believed to be passed on by spirits they have made contact with. 
Extreme sadness for example, desperation and anger are all commonly associated with paranormal experiences. Quite how these emotions come to be, and how they later manifest is open for interpretation, but for those who are going through them, they are very real and very disturbing. It is logical that for some people, these feelings and emotions will linger, possibly causing them, over time to slip into darker feelings, which can become consuming.