Religious conversion is the act of joining a religion. The exact definition is hard to specify exactly because of differences in religious practices. Infants are usually excluded from the definition. Major denominations claim to have tens of thousands of converts every year. 
Research into religious conversion has some serious shortcomings in that it often depends on self reporting and asking converts to reflect on their past, which may not give an accurate picture. Also, surveying people already in a religion biases the sample group because religions may be attractive to particular types of people. This may be overcome with longitudinal cohort studies. 
The opposite of a religious conversion is apostasy.
What type of person converts?
Converts often report stressful childhoods and adolescence, and difficult relationships with parents. 
A longitudinal study by Kirkpatrick  found that adults with certain adult attachment styles, relating to how they perceive their own relationships, were more likely to report a "new relationship with God". This effect was evident for those who worry about not being loved by others as much as they would like ("insecure-anxious"), and those that are comfortable without intimate relationships ("insecure-avoidant"). This may indicate religion is a compensation for the lack of secure relationships.
Some people may desire behavioural change and see religion as a means to do it. The Jesus Movement attracted many former recreational drug users who effectively used the social support of the church as a "half-way house".
- "certain types of personalities may be more prone to religious conversion than others, and the religious group may be for them a vehicle through which they express it."
Process of conversion
Each religion has different customs and expectations of converts. While the process of conversion in general is still being studied, Rambo  suggested conversions tend to follow the pattern of:
There is some evidence that potential converts agreeing to adopt certain beliefs in return for group membership, which comes with social acceptance and support.
- "More often, a preoccupation with self, and a state of emotional turmoil rooted in the particular circumstances of the person's life dominated the [religious conversion] process. "Objective" questions about the principles or the theology that underlay the old or new creeds were absent from the stories of most of the converts I interviewed "
Impact of conversion
Personal strivings, concerns and identity
Anecdotal accounts of religious conversion suggest a significant change in a person, which should be observable. Adult converts often experience an intensification of religiosity to a point that they are more religious than lifelong members. There is evidence that religious conversion can profoundly effect a person's values and goals. 
Conversion to a religion is often but not always accompanied with a sense of new purpose , peace and joy but many also be accompanied with struggles with unwanted behaviours. Converts generally test higher on the Purpose in Life Test (PIL) which is a self evaluation on feelings of living a purposeful and meaningful life. In the PIL study, Fear of death was found to gradually decrease over the long term. 
Converts to new religious movements have been found to have reduced illicit drug use, less mental distress and a clearer sense of self.  The process of converting has even been compared to psychotherapy. 
- "[conversion] can result in profound, life transforming changes in mid-level functions such as goals, feelings, attitudes, and behaviors, and in the more self-defining personality functions such as identity and life meaning. "
Traits and temperaments
Most studies find that the basic underlying personality of a person, described by models such as OCEAN (Conscientiousness, Extroversion, Agreeableness, and Neuroticism), appears to be unaffected by religious conversion. A human's personality becomes fixed "like plaster" between the ages of 25-30.
- "the popular claims of dramatic changes in basic personality structure, by both those opposed to new religions as well as those who see them in more positive terms, do not seem to be warranted by the evidence. [...] conversion seems to have minimal effect on elemental functions such as the Big Five traits "
Not all studies conclude personality is unchanging though conversion; Halamaa and Lačnáb  found that self reported and independent rating of a converts personality indicates a change in Big 5 traits.
Do certain personality types gravitate to particular religions?
A study of 93 Hare Krishna (HK) members found the majority were in the “sensory, thinking, and judging” (STJ) category of the Myers-Briggs Type Indicator, which measures personality. Poling and Kenny (1986)
In Mere Christianity, C.S. Lewis speculated that Christianity might be more appealing to those with a greater awareness of their "sinful nature", which would make Christianity differ from the population in general (and not in a good way).
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Raymond F. Paloutzian, James T. Richardson and Lewis R. Rambo, Religious Conversion and Personality Change, Volume 67, Issue 6, pages 1047–1079, December 1999
- ↑ Kirkpatrick, L. A. (1998). God as a substitute attachment figure: A longitudinal study of adult attachment style and religious change in college students. Personality and Social Psychology Bulletin, 24(9), 961–973.
- ↑ Rambo, L. R. (1993). Understanding religious conversion. New Haven, CT: Yale University Press.
- ↑ Chana Ullman, Haven of Last Resort
- ↑ 5.0 5.1 Peter Halamaa and Mária Lačnáb, Personality change following religious conversion: perceptions of converts and their close acquaintances, Mental Health, Religion & Culture, Volume 14, Issue 8, 2011
- ↑ Paloutzian, Raymond F., Purpose in life and value changes following conversion, Journal of Personality and Social Psychology, Vol 41(6), Dec 1981, 1153-1160.
- ↑ Robbins, T., & Anthony, D. (1982). Deprogramming, brainwashing, and the medicalization of deviant religious groups. Social Problems, 29, 283–297.
- ↑ Kilbourne, B., & Richardson, J. T. (1984). Psychotherapy and new religions in a pluralistic society. American Psychologist, 39(3), 237–251.