While some people find their lives ruined by belief in imagined conspiracies that affect them personally - they may isolate from, or even attack, friends and family, and get diagnosed with psychosis - many other people believe in conspiracies on the basis of little evidence, yet have prominent places in society or even bodies like the US Senate.
Yet it seems clear to me that the same dynamics are often involved in both. The recent article, Why People Believe in Conspiracy Theories suggests we need to better understand the needs that are filled by conspiracy theories, and I believe such an understanding would be useful both in addressing political and social dynamics and in creating better mental health services.
One obvious purpose of beliefs in conspiracies is that they allow us to maintain the stability of our behavior patterns when we get information that would otherwise cause us to interrupt our behavior. Sometimes of course maintaining stability can be a good thing, other times not. If I am investing in a company for example, and someone tells me the company is about to collapse, I may suspect that the information about the imminent collapse could be simply a conspiracy to get me to sell, and decide to keep my money where it is, to maintain stability. This will end up being a good decision if the information about the company collapsing turns out for whatever reason to have been incorrect, but a bad decision if the information was correct.
In short, it can be costly to change our minds all the time, so belief that information that contradicts what we are doing is the result of a conspiracy can help us avoid those costs. It can also lead us to disaster when the information that challenged us turns out to have been true.
Many Democrats decided 9/11 was a conspiracy, probably because they didn't want to get sucked into supporting costly national changes designed to confront terrorism, just as many Republicans decided global warming is a conspiracy, because they don't want to support government regulations designed to combat it. In each case, the conspiracy belief serves a need by providing a justification for less reactivity to a perceived threat, but also in each case, there is plenty of danger that can result from belief in the conspiracy if in fact it does not exist.
Belief in conspiracy can also help ward off bad feelings. Maybe it's not that the music I'm producing is bad or unpopular, it's just that the music companies are conspiring to suppress it. Maybe we aren't really destroying living conditions for future generations on this planet, it's just that environmental wackos are conspiring to make us doubt ourselves. There's research connecting paranoia with self esteem, and in particular with fluctuations in self esteem.
Another good reason for developing conspiracy theories is simply to develop the ability to think independently, to remember that appearances can be deceiving. The preponderance of the evidence may point in a particular direction, but this is not proof that such a direction is accurate: there could be hidden factors, hidden manipulation, which led to the apparently convincing appearances. Conspiracy theories can provide us with some alternative viewpoints, ways of thinking other than just robotically believing appearances and going along with consensus views. Such independence of mind can be valuable, though also very hazardous if one simply slips into robotically believing in the conspiracy theory rather than just seeing it as one alternative view among a huge number of alternative possibilities, of which any one, or none, may be true.
There is also of course the need to detect conspiracies that may actually be present in our world. Failure to look for such conspiracies can lead to giving way too much credence to systematically produced misinformation, such as the misinformation drug companies have created in order to over-promote, and to minimize the hazards of, their products. People who are more on the lookout for conspiracies are more likely to be on the cutting edge of those who detect actual conspiracies that do exist.
Of course, people who have been betrayed in the past are much more likely to be on the lookout for more conspiracy. This may be an advantage to them when operating in environments where betrayal is likely, but also may be highly dysfunctional when operating in environments where appearances can largely be trusted and where good allies are available if one only trusts in them.
The belief that the world is organized in the form of a conspiracy against us at least contains the notion that the world is organized: that may seem more comforting than the notion that the world has no order, or the fear that it may have an order which is unknown to us. If we tell ourselves we know about the conspiracy, we can feel at least somewhat in control. Of course, if we organize our lives in response to a conspiracy that doesn't exist, the actual effect may be to throw our lives further out of control.
Normalizing paranoia and conspiracy theorizing, looking at it as both dangerous yet also an understandable and even sometimes constructive response to normal human dilemmas, is much more helpful than the psychiatric view of looking at it as "illness." I look forward to the day when everyone involved in mental health will routinely be trained in such normalizing understandings, and in how to talk to people about the dilemmas we face when we attempt to discern the truth, replacing today's unhelpful training in diagnostic labeling and narrow bio-medical conjectures.
(All of this is not to deny that some physical health or biological factors can influence how paranoid people are: it is known that various drugs for example can increase the likelihood of being paranoid, and drugs that amplify dopamine in the brain sometimes increase paranoia, while those that block dopamine can sometimes reduce it. Like the broader phenomena of fear and anxiety, paranoia is related to biological processes but is also way too complex to be classified as simply a biological mistake: instead it is more like a process or strategy that may be helpful or not depending on the specific circumstances.)