Like many other types of human behavior, suspicion is not easily defined or characterized. One basic definition states that suspicion is ¡°a feeling or thought that something is possible, likely or true¡±, though more often the term is used to define someone¡¯s mistrust and doubt over information that is presented to them, without the proof needed to know what is actually true. Another definition states suspicion as the ¡°act of suspecting¡±, which implies a certain amount of belief in something without sure proof.

Sometimes it is easier to define a term by building what we know from the ground up, but in the case of defining suspicion, it is a good idea to separate the concept from similar concepts that are often wrongly intertwined. There are many similar concepts to suspicion which many people incorrectly think as being the same as suspicion, and paranoia is the most obvious example.

Paranoia is a disorder and a psychological term used to describe intense feelings of suspiciousness and mistrust. Paranoia often involves the belief that there are others out there that want to cause harm. In severe cases the disorder can completely incapacitate the patient, causing significant distress and preventing the patient from being able to lead a normal life.

Paranoia can present itself as an obsessive attitude towards privacy, or it can revolve around a persistent delusion, where the patient sincerely believes in something that is not true or is not readily identifiable by other people in society. A key feature of the disorder is the failure to accurately read emotions on other people¡¯s faces, and to draw negative conclusions from situations that are neutral and open to interpretation.

Suspicion is a cognition that comes with many negative connotations, but like every other evolved human behavior, suspicion can be a very useful (and perhaps very important) trait. For example, it can help us to keep our belongings safe, make better social judgments, and adapt better to difficult situations. Psychologists agree however that there comes a point where suspicion stops being a useful trait and starts having a negative impact on our lives, and if suspicion becomes very severe and starts affecting daily life, this could be paranoia. Just like paranoia, suspicion does not only affect people who have an identifiable pathology; there is a continuous spectrum of symptoms and severities for people in all walks of life.

Suspicion is a very common cognition with people who suffer from paranoia, but it does not necessarily imply paranoia. What usually separates simple suspicion from paranoia is the intensity and frequency of the suspecting thoughts, and what separates mild paranoia from a clinical disorder is the strength at which the underlying ideas are believed. You might not be paranoid if you think that there are a certain people who are out to get you, but if you believe that there is a focused and concerted effort to hurt you by a non-specific entity or group, then you could very well be paranoid.