Image copyright Renee Linnell Image caption Renee Linnell: "Joy started coming back into my life"

Last Monday, US actress Allison Mack pleaded guilty to charges linked to an alleged sex trafficking operation in the suspected cult Nxivm.

Pronounced 'nexium', the group started as a self-help programme but its leader is accused of overseeing a "slave and master" system within it. Prosecutors also allege members had to pay thousands of dollars for courses to rise within its ranks.

But what leads people to join such groups? And how do they reintegrate into society once they leave?

You may find some of the details below distressing.

Renee Linnell

I was a dancer until a meditation seminar turned my life upside down

From the outside looking in it looked like the perfect life. I grew up in Florida and on a boat in the Bahamas with my parents and twin brother, but I always felt empty inside and sad. I didn't really fit in. Most of my family died before I was 15 and then my father died. I was always seeking for what happens after we die, why are we here?

When I was 33, I wandered into a tantric Buddhist meditation seminar and I sat down to meditate. I was expecting an older woman with long grey hair, a white robe and spa music. Instead it was a young woman and what looked like an Armani business suit and stiletto heels.

She put on techno music and she said "let's meditate" and put on her sunglasses. I closed my eyes to meditate and had this incredible experience. Everything goes white and there's so much peace. I realised this was what I had been searching for my entire life. I thought: "I don't care who this woman is, I don't care what she says, I'm home."

It took a while but now I realise it's like any toxic relationship. If you go on a first date and somebody hits you, you don't go on a second date. But they start with the romance, they seduce you, lure you in and that's what they did.

Then what happens is they start giving you so many tasks that so much of your time is consumed in the group that you start distancing yourself from friends, family and activities you loved. Without realising it, my support structure started to disappear and the groupthink started to set in.

Then, after the two-year mark, they started introducing self-doubt.

They would say you're evolving into this enlightened version of yourself. Everything from the old you no longer applies. They'd say it's just like an alcoholic. Once an alcoholic gets clean they can't really hang out with their old drinking buddies at the old bars.

The more money we made, the more money we paid. They'd justify it by saying everything is energy, including money. The more money you spend and give to the teachers the more empowerment you'd get.

It was all abusive, my whole life was theirs. Then the guru seduced me as a consort, where a spiritual teacher takes his student as a lover. He slowly but surely started criticising me. Nothing I did was good enough.

With cults, like any abusive relationship, the red flags are there all along and denial is such a powerful thing. The teachers would say: "Your ego is so big you don't want to change" and I would explain I did want to change and become enlightened, not even really understanding what enlightened meant.

Eventually everything came crashing down. I was at rock bottom and then had a near-death experience snowboarding and after that I started to hear clearly but didn't want to admit it to myself.

Almost seven years after I joined, I allowed myself to realise.

It was really hard at first. I left New York and moved to Colorado and thought I'd move someplace quiet and I'd be fine. Instead, I fell apart even more and pretty much couldn't leave the house. I was suicidal, barely eating, sleeping all day for six months.

Then joy started coming back into my life. It really took me five years, only recently in October, to feel like I was reintegrating.

Sarah Lionheart

I was held captive by a guru in India

Image copyright Sarah Lionheart

I was doing my PhD in consciousness and spirituality. I went to a talk and there was a Hindu monk talking very eloquently about consciousness and the mind so I started training with him.

Before I knew it I was completely hooked. Then he said: "I can't teach you any more, you need to go to my guru in India who's absolutely enlightened. This is your chance."

The reason I was vulnerable was that my own childhood had made me long for a family where I actually felt that I mattered and this was very much sold to me. I was aware that I wanted to get rid of the pain I was carrying emotionally.

After three days at the ashram in India, I'd eaten lunch and I remember slowly, slowly trying to hang onto the wall and my fingernails scratching the wall, slipping down and losing consciousness. The next thing I knew I was in the room they had given me and he was on top of me. I didn't get out of that room for three months.

The thing that confused me when I came home is that I couldn't explain to people what had happened. He'd be on top of me, I'd freeze, disassociate, and an hour or two later I'd be sitting there thinking: "This is not what I came here for, I thought he was supposed to have my best interests at heart."

Then he'd accuse you of not behaving properly. You wouldn't believe the mind tricks they play. He'd say: "It's because of your Catholic upbringing that you don't like this."

That was Autumn 1987. Eventually I realised I was probably going to go mad and die there if I didn't think of a really good plan.

My first attempt to escape didn't work and it made things worse, so I pretended to him that I thought it was wonderful that I was there. I said: "Look, you want the monk from England to come over and your second favourite, NV Raghuram from Bangalore, and we can all celebrate that I'm your consort and how wonderful this is." He believed me.

Eventually these two came and I explained to the English monk what was happening. I also said: "I've lost loads of weight, I'm ill, I'm sure my mind is beginning to go and I need help." He replied: "You have to do what the guru tells you to do, always."

I thought at that moment: maybe I have got it all wrong.

The next night I talked to the monk from Bangalore, NV Raghuram, whom I had never met. I had to say: "Look, I'll be in the bathroom at this time if you'll come and talk to me." When I told him, he explained this had happened before, and they had hoped the guru had stopped. He got me out of there and he looked after me.

He told me about the girl it had happened to before had been the same age I was. She'd gone insane and been put in a mental hospital. Her brother who had walked in on it had hung himself.

What people don't understand is when you sit in front of a man or woman with all the pomp and all the incense... and they say you need to be more loving and kind and do these prayers and help all sentient beings, you feel your heart open, you feel: "Yes, I want to be that pure person, I am so grateful to you."

That very pure open feeling is actually all your own doing but you think this guru has done something to you.

For me, the coercive control was really relentless - 24/7 - and the dynamics of manipulation and gaslighting were similar in my family of origin, so it all felt very familiar.

If you are emotionally secure with a secure childhood where you felt like a cherished and important person and that your feelings were genuine, I think you wouldn't be so easily hooked.

Image copyright Empics

How do you help someone who is in a cult?

The Cult Information Centre, a UK-based charity that gives advice to cult members, their family and friends, offers 22 "do's and don'ts" to people who want to help a loved-one.

Among them:

Always welcome the cult member back into the family home no matter what is said

Record all the names, addresses and phone numbers of people linked with the cult

Do not say: "You are in a cult, you are brainwashed"

For more information, read here

Jane Rickards

I thought he was God

I had warring parents growing up, so it wasn't that secure. I became very afraid of ghosts and things like that because my older brother and sister had said they'd seen ghosts. I was the younger one and had become very frightened.

I later started to check out who was speaking about 'spiritual matters' in London and that's how I came across the person who sucked me into his horrors. He was advertising himself as an American-Indian shaman. I was just being curious, I thought.

Image copyright Jane Rickards

I went along to the first meeting and was fascinated because I imagined this old grey man in a beard, full of wisdom, coming to the stage. But it was a young guy, American, long hair, hippie-type and the message was peace and love. It was amazing.

I spent two to three months just on the back benches. Then I got a bit bolder and asked him about a friend I was concerned about. This was the first time I'd had proper eye contact with him and I could feel myself just melting with these great big eyes full of compassion. He said: "Don't worry about her, she's fine. You're the one who can really help me a lot." That was it.

Soon my mind was controlled by him; I'd lost all connection with the outside world. I'd lost contact with my family; I'd given him money and very quickly said I was his wife.

Then the sex started, which of course I didn't want, but I had to because I thought he was God by then. There was no doubt in my mind that he was at least Christ or Buddha.

We were travelling a lot and very quickly I started to have panic attacks and started getting really sick. In about a year I lost the plot completely.

I made one attempt to kill myself but he had actually warned us before to not ever try killing yourself because he would be on the other side waiting and it'd be even worse. That was the only thing that stopped me. I learned after there had been previous suicides in the group.

It always boiled down to him putting us through hell in order to cure demons so we could become effective human beings that could help him save the planet. He was mostly drugged up and we had to take drugs. I mostly just took dope but the men had LSD. I once took LSD.

I'd initially been kicked out because I was costing them money medically. I escaped to the country and held up there for the winter to get myself better and by the spring I was desperate to get back in because I still thought he was God and I was just not good enough. I actually did that but then I realised I'd had enough exposure in the outside world and wanted to leave.

The first three days after leaving I was on a high because I thought I was free. They call that the honeymoon period. After that I deteriorated mentally to the point of having a total mental breakdown. I tried to reintegrate but totally lost it and couldn't get out the door for some months. I was in a terrible state.

I was still trying to understand what fear was and I was still in the grip of thinking I was not strong enough to overcome it. I was so susceptible to his manipulation - on the one hand saying that I was strong and on the other saying that I needed help and wasn't good enough.

I received clinical psychology and professional mind control de-programming which was very useful in debunking this myth of power control.

Daniel Durston

I was born into a cult

Image copyright Daniel Durston Image caption Daniel Durston kneels by the grave of his brother Alex

For us I think it was the emotional, psychological and mental abuse which did the most damage. I think my particular family - and this was even said by one of the cult ministers - was very extreme. It just made it more menacing when parents could justify their actions by cherry-picking verses and I get why half of my siblings have just left and said they want nothing to do with God.

Mr brother Alex was quite like me, very questioning. But, you see, this cult keeps you conformed. Conform is a word that has always troubled me. When we have to conform it's a problem. In having to conform; going to these meetings three times a week, looking our best, not growing up with a TV - Alex was like a spring that just wanted to be uncoiled.

Alex was 23 when he took his life.

At the funeral, I remember [a cult leader] saying something like 'He's saved! Now he's going to heaven.' On merit of what? Because he's ceased to breathe? Because his heart has stopped? That's religious garbage.

They have this weird belief in the cult that when you die, that's somehow when you're saved. The problem with that is: what kind of psychotic God, once you're alive, says: 'Sorry you're not saved yet.' It's just weird and it doesn't make sense. A lot of cults do this and this is how they exert control on people.

I've been through counselling but I realised there was a chasm. This was a very trained counsellor in trauma, sexual abuse, alcohol abuse - I even paid a bit more - but I realised this was one thing where she was out of her league. She just couldn't get it. A cult isn't just a set of religious doctrines, or interpretations, it's a way in which a person is conditioned socially. They train you to be socially retarded.

One common thing with all of us siblings is that we were aimless. We weren't encouraged in education, we weren't encouraged in any talents we had. They weren't cultivated.

I left when I was 26 in New Zealand. My parents reside in Arizona and we have very little contact. They show no interest in me, my wife or children.

With physical child abuse, it's wrong but it can be named, it can be shamed and you can seek healing and a road to restoration.

But with the cult, every aspect of the holistic beings we are is violated. Where do you start with such a mess? How do you start to unpack that without falling apart in the process?

(Interviews have been edited for brevity and clarity)