'Gang violence affected my mental health'
Police estimate there are around 200 gangs in London, with the number of knife and gun incidents reflecting the level of violence involved. But the mental-health impact of gang violence is much less understood.
Lucy is 26 and already she has lost 10 friends and relatives from gang violence.
She saw her first murder when she was playing in a park on a Sunday afternoon. Three gang members appeared and a fight broke out.
"I see my cousin on the floor with a screwdriver in his head and he died later on in hospital," she tells the Victoria Derbyshire programme.
In The Mind - a series exploring mental health issues
Explained: What is mental health and where can I go for help?
Mood assessment: Could I be depressed?
Lucy had thought she was growing up on a nice, quiet estate in Brixton, south London.
"Suddenly I learned about this life I never knew existed - always getting a call, or just hearing months later or sometimes immediately... that someone else has been killed that I know. It just made me more and more sad. That's when I started to get depression.
"If a year went by that someone didn't die, that was a good year, cos you ain't lost someone."
The most recent figures from the London Ambulance Service show 167 people were injured in knife incidents in the capital in October last year, while nine were injured by guns.
Metropolitan Police figures show there were 292 incidents of knife crime causing injury last December, and 302 in November.
Lucy says the incident that sticks in her mind is the murder of Zac Olumegbon, who was stabbed to death in front of his school in West Norwood, south London, when he was 15. Four teenagers were jailed for life for his murder.
"I got a ping on my BB [phone] to say he'd been killed. That had a really bad effect on me for at least a year. I was just so upset, depressed, couldn't sleep," Lucy says.
"I was thinking of what he must have been going through at the time of being chased and going to school and ending up being killed. It was just really sad for me."
There is very little research on the mental-health impact of gang violence, but a 2013 study of 108 gang members found half had an anxiety disorder, more than 85% a personality disorder and 25% screened positive for psychosis.
Prof Jeremy Coid, lead study author, said exposure to violence was the likely cause of their mental-health problems.
Lucy says gang violence affects particularly the young, black, inner-city community. For her it sparked symptoms of post-traumatic stress disorder.
This can include flashbacks, nightmares or physical sensations such as pain, sweating, nausea or trembling.
"Something could trigger off a memory. Even going past an area, someone saying something, just brings flashbacks. I've had sleep problems ever since [Zac's death] for the past five years, to the point I've had to take medication," she explains.
"I'm definitely anxious, for example, when I go to nightclubs and see people getting into an argument. Straight away I think: danger, someone has a gun, a knife. And immediately I will leave."
'Someone to talk to'
Her first encounter with mental-health services was when she was 14 or 15. She was given tablets and one counselling session. "Then it's like you get lost in the system."
She adds: "Then another death happens, then you feel worse so you carry on drinking, getting into more trouble. And then the killings just keep going on and in the end I just felt like I was going to have a breakdown."
Lucy says the authorities need to acknowledge that gang violence creates a lot of mental, as well as physical, trauma, and counselling should be much easier to access.
She would like to have "someone to talk to, often."
"When it's your family, it's such a hard thing to sit there and talk about. Someone giving you the time, and showing you that they're there to listen, and care what you have to say. When people feel that no-one cares, that's when people get angry and just make bad decisions," she explains.
Lucy says she is offered only tablets, and the waiting list for help is four months long.
"I just feel in that four months, anything could happen. You could end up killing yourself or being killed, especially these young men who need help, but they're too ashamed to ask for the help," she says.
The Victoria Derbyshire programme is broadcast on weekdays between 09:15 and 11:00 on BBC Two and the BBC News channel.