This disorder is considered pervasive, inflexible, and enduring pattern of distrust and suspiciousness of others with millon referring to it as "suspicious" pattern:

"Paranoid Personality Disorder".

Explanation:

According to my research based on various Psychological studies, the disorder described in the question is called  "Paranoid Personality Disorder". This is considered as a mental disorder that (like stated in the question) makes the sufferer full of paranoia and distrust of everyone around them.

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