What do you call someone who doesn't seem to have a general sense of right and wrong, doesn't care about others, and thinks nothing about lying and manipulating to get what they want? A jerk, perhaps? Now, what would you think if that same person is also immensely egocentric, impulsive and violent, hurting other living creates for fun?

If you're able to get away from such a person without any harm, that's all you need to know. Not everyone is that lucky. The diagnosis that comes with this description is Antisocial Personality Disorder, and there's more to it than meets the eye. Are you currently dealing with someone with someone like this? Arming yourself with information can help.
Impairments In Personality Functioning
People with Antisocial Personality Disorder show impairments in self-functioning. That can mean they they have a distorted sense of who they are — they're egocentric, and get kicks from power, money, other or forms of personal gain. It can also mean that they're are so unconcerned with the social standards of the society they live in that they don't think twice before breaking the law, and that they are preoccupied with personal gratification.
These people also lack empathy. That doesn't necessarily mean that they don't know what emotions others experience, but it does mean they don't care. They don't feel sorry while they are doing things to hurting or mistreating others, and they don't feel guilty afterwards either. Because they don't relate well to others, the intimate relationships of people with Antisocial Personality Disorder are based on exploitation. They may coerce, pressure, or trick people into being close to them.
Pathological Personality Traits
People with Antisocial Personality Disorder display a range of what the Diagnostic and Statistical Manual of Mental Disorders (DSM) calls "pathological personality traits". They have so many nasty traits that the DSM-5 breaks them into multiple domains!
Manipulativeness, deceitfulness, callousness and hostility all fall under "antagonism". In practice, this means someone with Antisocial Personality Disorder will slyly lie, charm, or butt-lick their way into getting what they want. Misrepresenting who they are is the norm, and they don't care what others feel or need — as long as they achieve their goals. They don't feel sorry or guilty and can be cruel and sadistic. In addition, these people may also be quick to anger and seek revenge.
See Also: How To Recognize People With Narcissistic Personality Disorder
Irresponsibility, impulsivity, and risk taking are also characteristic of those with this personality disorder. These traits fall under "disinhibition". They don't take the promises they make seriously, can be financially irresponsible, and just don't think the rules that apply to others were made for them. Danger makes them feel great, and they may think they're invincible and get themselves into risky situations on impulse, just to counter boredom.
Dealing With People Who Have Antisocial Personality Disorder
Nasty As The Norm
The traits and behaviors characteristic of Antisocial Personality Disorder don't just pop up occasionally, when the person is having a bad day or facing a stressful situation. To qualify for this diagnosis, the person has to display these symptoms consistently over time, across a wide variety of situations. Being a dangerous, toxic jerk is the norm for these people. They've been at it since at least early adulthood and probably displayed symptoms even before that.

What Causes Antisocial Personality Disorder?
Antisocial Personality Disorder is probably a unfortunate combination of nature and nurture, like other personality disorders. Numerous factors contribute to the making of someone with this disorder. Though people younger than 18 can't be diagnosed with Antisocial Personality Disorder, they do often already show signs and they may be diagnosed with Childhood Conduct Disorder.
Being abused (mentally, physically, sexually or a combination) in childhood is one risk factor. Other traumatic childhood events and a family history of substance abuse and mental illness are other risk factors. That does not mean you should suspect everyone who has lived a hard and unpleasant life — rather, limit that suspicion to people who actually display symptoms.
Can It Be Treated?
Antisocial Personality Disorder can be diagnosed after a thorough psychological evaluation, often in combination with a physical examination and blood tests to rule out other causes of the symptoms being displayed. Psychotherapy can be useful, as can certain medications to control specific symptoms of the disorder, like aggression.
These people don't think there's anything wrong with them, and are likely to get rather stroppy if you suggest they need treatment. When people with Antisocial Personality Disorder are forced to find themselves face-to-face with a psychologist or psychiatrist — because they're in prison, for example — they will try to manipulate their healthcare provider into idolizing them, or else just get angry.
What If (You Suspect) Someone You Know Has Antisocial Personality Disorder?
If they're a vague acquaintance or brand new to your life — run! If they're a fairly distant relative you're not in a close relationship with, try to avoid them. If that's not possible, get therapy for yourself to learn coping strategies. If they're a co-worker, try to avoid them. If they're your boss, look for another job.
See Also: The Key Differences Between Bipolar Disorder And Borderline Personality Disorder
The same goes for people who think their parents, siblings or other close relatives could have this disorder. Exiting a relationship with someone with Antisocial Personality Disorder is complex, because it can be dangerous. This article can't deal with the complexities of that situation. You will benefit from the help of a mental health professional with a lot of experience in dealing with Antisocial Personality Disorder, as well as the help of a safety expert. (Look up Gavin de Becker, who has very sane things to say about dealing with dangerous people.)
- Photo courtesy of Katie Tegtmeyer via Flickr: www.flickr.com/photos/katietegtmeyer/4158902321