This is a question that surfaces periodically among new clients. The answer? It all depends on how you define "personality." Personality differs from skills or competencies. Skills are tools for getting jobs done. Personality is that set of deep, basic traits that uniquely determine how we perceive experiences and influence our motivations and behaviors.
Researchers generally agree that personality can--and does--change until about age 30. There's a lot less agreement about what happens then.
Researchers usually agree that--at a basic level--five main aspects of personality stay fairly stable throughout our lives. Think of these aspects as tendencies. Sometimes the tendency is small, other times moderate, other times very strong.
Neuroticism--persons who score high on this trait tend to be anxious rather than calm. They're also more likely to be angry, depressed, self-conscious, impulsive and stressed. Not all of those at the same time, but one, maybe two characterize a person's personality. I have one delightful client that I've known and worked with for years. He's highly impulsive and all of his people know that, and factor that into how they relate to him. He knows it too, and since he's the boss he doesn't work at becoming less impulsive. He knows everyone of importance knows. On occasion he's asked me to warn people about his impulsiveness. BTW: He has a highly successful history and his people make the adjustments for him.
The other end of the continuum of neurosis is psychosis. The difference between the two at the extreme is obvious: neurotics "see" more than is really there, and psychotics don't see what's going on at all. There's plenty of neuroticism among business people, but psychotics don't last long in any career.
Extraversion--high scorers are friendly, outgoing, assertive, energetic and optimistic. I'm an extrovert and I enjoy extroverts. But I wouldn't want to be on a team or in a group that is filled with extroverts. The noise would drive me nuts. Introverts leven the field and make a very significant contribution to the workforce. If I were a team leader, the first choices I'd want would be a couple smart introverts.
Openness to experience--a high score indicates a vivid imagination and an appreciation of art and beauty. Such persons welcome new ideas and may question traditional values and beliefs. Low scorers tend to be conservatives who accept authority. Where would you place Dick Cheney on that continuum?
Conscientiousness--persons strong in this area are competent, orderly, self-disciplined, motivated and careful. High scorers may become workaholics, while low scorers may lack ambition.
Agreeableness--high scorers in this area tend to demonstrate a high level of trust, honesty, altruism, compliance, even modesty and concern for others. In his theory of development, Erik Erikson argued that trust was the first stage of human development, but that there needed to be a tension between trust and mistrust. Low scorers may be quite cynical. Too much agreeableness, represented by beling overly trusting and compliant, can impact your creativity and entreneurialism. Of course, identifying the line between too much and too little agreeableness can be tough, requiring long-term feedback and personal observation.
These characteristics are relatively stable, particularly after age 30. They are most likely determined by both nature and nurture. That leads me to suggest that personality change can come about. Some researchers think that it occurs through the "crystallization of discontent." What happens is that isolated negative events gradually get connected in our thinking. That could include tragedy, recurring negative feedback, a series of failures, etc. Change happens when that vague discontent gets focused.
After a discussion of this sort with clients, one question usually follows. What is the best set of personality characteristics for business success? Certainly the extremes can cause difficulty. But in the right situation even extremes can work to your advantage. Quite a few years ago, a law firm engaged my services as a last ditch effort to assist a partner in dealing with his angry outbursts. During the second coaching session, the lawyer told me that he'd struggled with paranoia (a neurotic condition) for years, worked with a psychiatrist on numerous occasions, and he was fearful that his outbursts couldn't be managed. I was clueless about whether they could be managed and told him that. But I was also curious as to what he saw as the "upsides" of paranoia. He was shocked by the question and quickly responded that there was no upside to paranoia. I disagreed strongly, especially in his career as a corporate lawyer. His most basic task was to keep clients out of difficulty. That required a great deal of insight as to what are all the possible bases on which a client/firm might be sued or challenged and end up in litigation. My assumption was that aside from his education and intellectual ability, his paranoia was a highly useful disease. He had no difficulty seeing more danger than was probably there. That single insight was almost immediately liberating. It was a thought that had never crossed his gray matter. Obviously the insight was exceedingly useful. He continues as a partner in his firm and has rarely had an episode in the 15 years since.
Can you change your personality? Yes, but slowly and with great care.