Nihiliphobia
Nihiliphobia was a psychological condition which described a literal fear of nothingness. Symptoms included dizziness, nausea, and unspeakable dread.

In 2375, when the  entered the star-less region of space known as "," Neelix discovered that he was nihiliphobic when faced with the unending blackness of the area. This caused him to experience a panic attack, necessitating treatment by The Doctor. In an attempt to make Neelix feel better, The Doctor informed Neelix that he could relate to his problem, as he went into an empty oblivion every time he was deactivated, but Neelix responded that The Doctor was being less than helpful. ()

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Psychological conditions