They’ve given you no reason not to believe them, but as you reflect back you can’t help this nagging pulling toward questions and relentless suspicions. Of course, it could be your gut that’s telling you they’re lying and untrustworthy, or could this paranoia have something to do with your genes? In the question of nature versus nurture, scientists tend to favor the combination of both genetics and environmental impressions, but paranoia is categorized into psychotic experiences and little is known on the degree of genetic or environmental susceptibility.

Are paranoid people born that way or are they simply a product of a fear-induced upbringing? A team of researchers at the University of London examined nearly 5,000 pairs of 16-year-old twins in order to figure out if it was genes or the environment that was driving their paranoia, and published their findings in JAMA Psychiatry. Family members share so many different types of genes and similar experiences, but by using fraternal and identical twins, it would be easier to separate the two apart.

Identical twins will have the same exact genetic makeup, which means if psychological traits are more alike in identical twins than fraternal, it’s likely the trait will be gene-related. By just reviewing the collection of twins, researchers could extract the similarities in identical twins and found 50 percent of paranoia cases were hereditary, while the other 50 percent were affected by a combination of environmental factors from experiences indicating humans are more a product of their environment more than any other factor.

Genes play a large part in our mental health, but researchers concluded it is actually the environment and upbringing of a child that determines if they are going to be paranoid for the rest of their life. And it’s not just paranoia people have to worry about, but it is also the manifestation of schizophrenia, which at its most severe cases will lead to hallucinations and a whole slew of complicated symptoms and irregularities.

Yes, we can have the alcoholic gene, but that doesn’t necessarily mean we’ll become alcoholics, it simply means we’re more susceptible to falling into alcoholic patterns. If there is a gene for paranoia, it hasn’t been discovered yet, but the twin study does point toward a genetic marker. It’s just a matter of time until scientists discover the marker, which will tell a person they have inherited the paranoia gene, or they’ll eventually prove your incessant questions and mistrustful behavior is learned from experience.

It may be more of a cause of post-traumatic stress disorder, in which your trust was so scornfully misused you have become suspicious of every single person standing in front of you from there on out. Fool me once, shame on you. Fool me twice, shame on me, except the latter isn’t going to happen because you’re too paranoid to give another person the opportunity to hurt you.

People with a paranoid personality disorder generally have a long-standing distrust with all people they come across despite being given a reason to suspect them of anything. A personality disorder is an enduring pattern of behavior that typically leads to significant problems in their social, personal, and work lives. It could be caused by a combination of biological, genetic, and social factors, but a traumatizing event early on in a child’s life in which their trust was misused could be just as scarring as a malfunction in a person’s genetics.

Source: Ronald A, Zavos HM, Freeman D, Haworth CM, McGuire P, and Plomin R, et al. Consistent etiology of severe, frequent psychotic experiences and milder, less frequent manifestations: a twin study of specific psychotic experiences in adolescence. JAMA Psychiatry. 2014.