What Are the Different Causes of Paranoia?

Rebecca Harkin

Paranoia is an overwhelming feeling of fear and suspicion that manipulates a person’s thoughts and behavior. The causes of paranoia can be mental and physical illnesses as well as prescription and illegal drugs. The most common treatments include anti-psychotic or anti-depressant drugs and psychotherapy.

Paranoia can be caused by mental illnesses like Alzheimer's disease.
Paranoia can be caused by mental illnesses like Alzheimer's disease.

The most common mental illnesses that can produce paranoia are paranoid schizophrenia, paranoid personality disorder, and Alzheimer’s disease. Paranoid schizophrenia is a form of mental illness marked by psychosis or difficulty interpreting reality. Psychosis can cause people to misinterpret the actions of people around them, producing paranoid thoughts and behavior. Paranoid personality disorder is a psychiatric illness marked by continual feelings of suspicious and anxieties. Alzheimer’s disease is a progressive form of dementia that affects memory and rational thought processes, and sometimes patients feel and act strongly suspicious of caregivers and family members.

Medications may have paranoia as a side effect.
Medications may have paranoia as a side effect.

Other causes of paranoia are Parkinson’s disease, Huntington disease, strokes, and brain injuries. Parkinson’s disease is a neurological disorder leading to uncoordinated movement and shaking. The medication used to treat Parkinson’s disease will sometimes cause paranoid thoughts or behavior, and switching medication or manipulating the dose may help to control this side effect. Huntington’s disease is a degenerative neurological disorder that can produce paranoia as the brain loses the ability to reason. Rare causes include stroke and brain injury, both of which can produce either temporary periods of or lasting problems with paranoia.

Psychosis can cause paranoia.
Psychosis can cause paranoia.

Several prescription medications, such as the acid reflux medication cimetidine, the muscle relaxer baclofen, some corticosteroids, amphetamines, antidepressants, and medications used to treat the human immunodeficiency virus, can also cause paranoia. In most cases when paranoia manifests, the dose of the drug can be altered to control the paranoid side effect or a different drug can be substituted. One of the most well known causes of paranoia is the use of the illegal drugs 3,4 methylenedioxymethamphetamine or ecstasy, marijuana, lysergic acid diethylamide (LSD), phencyclidine (PCP), and amphetamines. Withdrawal from these drugs may also cause difficult periods of paranoia.

Treatment for paranoia will often involve the use of anti-psychotic or anti-depressant medications. When possible, psychotherapy can be tried for receptive patients, but the overwhelming fear and suspicious thoughts of paranoid people may prevent this form of therapy from working. Psychotherapy is sometimes possible after the patient has taken anti-psychotic or anti-depressant medications for a short period of time. In more severe cases, paranoia may be treated with electroconvulsive therapy or hospitalization.

Paranoia may cause an individual to misinterpret her environment and the actions of people around her.
Paranoia may cause an individual to misinterpret her environment and the actions of people around her.

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Discussion Comments


I went out with this guy for two years. He loved me and I loved him, but over time, I noticed his behavior became clingy and I found out afterward that he had been reading messages and Facebook private messages and claims that he had recordings of me in his house when I was there. I ended things because I was scared and worried, but I often wonder whether there was more to it. He had a very stress filled life and slept a lot.

I guess I didn't think much of it until it was too late. The night before he told me he bought me a voucher for a massage after my exams. It was so out of the blue for me.


@Pharoah - I'm surprised your doctor didn't tell you about all the possible side effects of the medicine you were taking. But you're right, no matter what causes paranoia, it doesn't sound pleasant.

I've actually never experience paranoia myself, but I have been around a paranoid person before. It was unpleasant and scary just being a bystander, because there was nothing I could do!


Paranoia sounds so scary, even for people that are just getting it as a side effect from medication. I've actually taken corticosteroids in the past, and they definitely don't warn you that steroids can cause any kind of mental side effects.

But guess what? They totally can! In addition to paranoia, they can cause anxiety, which is exactly what happened to me. It was really scary, especially because I didn't know it was a possible side effect until I took a look at the insert that came with the medicine from the pharmacy weeks later. By then I was feeling better, but the whole thing was really unpleasant.


@SZapper - It can be hard to get anyone who is having mental health issues into treatment! A lot of people who are having mental health troubles either don't think they have a problem, or don't want to see a doctor.


I imagine it must be really hard to get someone with paranoia to seek paranoia treatment. After all, since they're already paranoid, they may think the person who is trying to get them into treatment is conspiring against them!

It sounds like it's probably a lot easier to help someone who is having paranoia due to medication, because they're already under a doctor's care. At least then, the doctor is already monitoring their symptoms.


@Markus - The paranoid personality disorder you describe in your friend definitely sounds like the effects of heavy alcohol abuse. My advise would be to continue to help your friend and convince him to seek professional help as soon as possible.

Alcoholism is a serious disease that has the ability to destroy lives. Long term usage can lead to brain damage and even death. Ignoring it won't make it go away.

Your roommate needs to get control over his drinking so he can get down to the core of the real problem. His break-up with his girlfriend will pass much quicker and in most cases less damaging than the alcohol will.


My roommate has been on a drinking binge for the past couple of weeks now after a bad break-up with his fiancee'. I'm pretty concerned about his well-being and the neurological effects of the alcohol.

He's been late for work several times and every night he walks in with a case or two of beer which he consumes entirely on his own.

When I try and talk to him about his drinking he gets all paranoid with me and starts making strange accusations that just aren't true.

I really don't know what to do at this point, I mean he's a really good friend and he always covers his share of the bills each month. Since I've known him he's never shown any signs of paranoia before.

Do you think I should just back off and let him work it out on his own or could this lead to some kind of psychological damage if ignored?


My ex-husband and I battled with his symptoms of paranoia during our fifteen years of marriage. He has bipolar which I believe is the main cause of his schizophrenia-like symptoms.

For weeks at a time I would live under a hostage type situation because of his paranoia. I remember he often felt as though someone was watching him or that he was being followed.

I wasn't allowed to answer the door, walk our dogs or even take our children to the playground without a male friend for security protection.

It's very difficult living with someone you care about under those kinds of conditions.

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