What scratchme1010 wrote.
It has been said that people join religions to meet psychological needs (most times unbeknownst to themselves).
Nine factors have been associated with recruitment into cults - SOURCE: Factors related to susceptibility and recruitment by cults by Curtis JM, Curtis MJ. Psychol Rep 1993 Oct;73(2):451-60:
a) generalized ego-weakness and emotional vulnerability
b) propensities toward dissociative states
c) tenuous, deteriorated, or nonexistent family relations and support systems
d) inadequate means of dealing with exigencies of survival
e) history of severe child abuse or neglect
f) exposure to idiosyncratic or eccentric family patterns
g) proclivities toward or abuse of controlled substances
h) unmanageable and debilitating situational stress and crises
i) intolerable socioeconomic conditions.
Mental health issues can be involved in a person's turning to religion. For example, persons on the schizophrenic, Axis I or Axis II spectrum tend to exhibit religious intensification.
Also, intensification may be one of the coping mechanisms used to deal with distress/trauma, and is associated with the need to find meaning in the distressing event in order to avoid a breakdown of identity  or find relief from whatever is overwhelming them.
 Van der Lons, J. (1991). What is psychology of religion about? Psychology of religion. H. Malony. Grand Rapids, MI, Baker
It provides a list of DOs & DON'Ts.
It also provides some simple questions you can ask a loved one to get them to start thinking for themselves – which is always a good first step:
- What attracted you to your group in the first place?
- When you first joined, what did you expect to achieve as a member of the group?
- What have you achieved?
- What do you hope to achieve in the future?
- What have you personally witnessed others achieve?
- How long do you expect it will take for you to achieve your goals?
People have been raised to believe that God cares for them, he solves problems and difficulties and he is watching over them every hour, every minute of every day. This gives them a sense of security.
Trying to wake someone up can feel like an attack on their sense of security.