An extreme self-involvement or undeserved high opinion of oneself. This will often get in the way of forming healthy relationships and the overall happiness of a person.
Narcissistic Personality Disorder
A disorder in which a person's self-involvement reaches the point where it inhibits normal social function and establishing meaningful relationships.
Negative Peer Groups
A group of friends that are involved in driving a teen or child towards poor choices. This is most common in young people as they are more susceptible to peer influence.
Negative Thinking
A pattern of thought that focuses on the perceived problems a person is experiencing. In the long-term, continually negative thinking can lead some individuals to develop depression or other mental health issues.
A form of therapy that focuses on identifying tangible problems in the brain that can be causing or contributing to disorders.

Neurotypical (an abbreviation of "neurologically typical") is a relatively new or esoteric term widely used in the autistic community as a label for people who are not on the autism spectrum. In other words, this refers to anyone who does not have any developmental disabilities such as some forms of autism, dyslexia, developmental coordination disorder, or ADHD.

An addictive stimulant that is present in cigarettes and many other tobacco products. Because it is highly addictive, it is considered very dangerous as it encourages continual abuse of tobacco.
Night Terrors
A sleep disorder that most commonly occurs in children. It is characterized by short bouts of extreme fear or panic.
Nihilistic Delusion
A mental condition where a person believes that nothing is real and both themselves and others do not actually exist.