Giving thought to why people find it so difficult to leave a toxic group, I remember about Oxytocin, the 'love/bonding hormone'. OC (oxytocin) is most well known for babies bonding with their mothers, sexual arousal, etc. But it also has a role in group ritual, religious ecstasy, etc. Some people produce more from their hypothalamus than others (devotees, followers, bonders) - others don't (aggressors, warriors). Lots on line about OC's role in behavior. But most pertinent find was right here on Cult Ed in the ISKON thread:
]oxytocin and cult behavior
So here we have a biochemical component to perhaps help understand the difficulty in walking away. People do become dependent on OC when taken pharmaceutically, but we produce it naturally under certain conditions.