Their (primitive) defence mechanisms include splitting (they view world – and people in it – as "all good" or "all evil"), projection (attribute their own shortcomings unto others) and Projective Identification (force others to behave way they expect them to).

The psychopath fails to comply with social norms. Hence criminal acts, deceitfulness and identity theft, use of aliases, constant lying, and conning of even his nearest and dearest for gain or pleasure. Psychopaths are unreliable and do not honour their undertakings, obligations, contracts, and responsibilities. They rarely hold a job for long or repay their debts. They are vindictive, remorseless, ruthless, driven, dangerous, aggressive, violent, irritable, and, sometimes, prone to magical thinking. They seldom plan for long and medium terms, believing themselves to be immune to consequences of their own actions.

(Adapted from my Mental Health Dictionary)

III. The Stalker as a Bully

Bullies feel inadequate and compensates for it by being violent – verbally, psychologically, or physically. Some bullies suffer from personality and other mental health disorders. They feel entitled to special treatment, seek attention, lack empathy, are rageful and envious, and exploit and then discard their co-workers.

Bullies are insincere, haughty, unreliable, and lack empathy and sensitivity to emotions, needs, and preferences of others whom they regard and treat as objects or instruments of gratification.

Bullies are ruthless, cold, and have alloplastic defences (and outside locus of control) – they blame others for their failures, defeats, or misfortunes. Bullies have low frustration and tolerance thresholds, get bored and anxious easily, are violently impatient, emotionally labile, unstable, erratic, and untrustworthy. They lack self-discipline, are egotistic, exploitative, rapacious, opportunistic, driven, reckless, and callous.

Bullies are emotionally immature and control freaks. They are consummate liars and deceivingly charming. Bullies dress, talk, and behave normally. Many of them are persuasive, manipulative, or even charismatic. They are socially adept, liked, and often fun to be around and centre of attention. Only a prolonged and intensive interaction with them – sometimes as a victim – exposes their dysfunctions.

(Based on an entry I have written for Open Site Encyclopaedia – Workplace Bullying)

The bipolar's swollen self-esteem, overstated self-confidence, obvious grandiosity, and delusional fantasies are akin to narcissist's and are source of diagnostic confusion. Both types of patients purport to give advice, carry out an assignment, accomplish a mission, or embark on an enterprise for which they are uniquely unqualified and lack talents, skills, knowledge, or experience required.

But bipolar's bombast is far more delusional than narcissist's. Ideas of reference and magical thinking are common and, in this sense, bipolar is closer to schizotypal than to narcissistic.

There are other differentiating symptoms:

Sleep disorders - notably acute insomnia - are common in manic phase of bipolar and uncommon in narcissism. So is "manic speech" - pressured, uninterruptible, loud, rapid, dramatic (includes singing and humorous asides), sometimes incomprehensible, incoherent, chaotic, and lasts for hours. It reflects bipolar's inner turmoil and his/her inability to control his/her racing and kaleidoscopic thoughts.

As opposed to narcissists, bipolar in manic phase are often distracted by slightest stimuli, are unable to focus on relevant data, or to maintain thread of conversation. They are "all over place" - simultaneously initiating numerous business ventures, joining a myriad organization, writing umpteen letters, contacting hundreds of friends and perfect strangers, acting in a domineering, demanding, and intrusive manner, totally disregarding needs and emotions of unfortunate recipients of their unwanted attentions. They rarely follow up on their projects.

The transformation is so marked that bipolar is often described by his/her closest as "not himself/herself". Indeed, some bipolars relocate, change name and appearance, and lose contact with their "former life". Antisocial or even criminal behavior is not uncommon and aggression is marked, directed at both others (assault) and oneself (suicide). Some biploars describe an acuteness of senses, akin to experiences recounted by drug users: smells, sounds, and sights are accentuated and attain an unearthly quality.

As opposed to narcissists, bipolars regret their misdeeds following manic phase and try to atone for their actions. They realize and accept that "something is wrong with them" and seek help. During depressive phase they are ego-dystonic and their defenses are autoplastic (they blame themselves for their defeats, failures, and mishaps).

Finally, pathological narcissism is already discernible in early adolescence. The full-fledged bipolar disorder - including a manic phase - rarely occurs before age of 20. The narcissist is consistent in his pathology - not so bipolar. The onset of manic episode is fast and furious and results in a conspicuous metamorphosis of patient.

More about this topic here:

Stormberg, D., Roningstam, E., Gunderson, J., & Tohen, M. (1998) Pathological Narcissism in Bipolar Disorder Patients. Journal of Personality Disorders, 12, 179-185

Roningstam, E. (1996), Pathological Narcissism and Narcissistic Personality Disorder in Axis I Disorders. Harvard Review of Psychiatry, 3, 326-340