A forensic psychiatrist says a rise in violence on Toronto's transit system signals an urgent need to better support people struggling with homelessness, mental illness and addiction.

Dr. Sandy Simpson, chair in forensic psychiatry at the Centre for Addiction and Mental Health, says it's impossible to know exactly what factors are to blame without knowing more about the suspects accused in recent attacks against TTC passengers.

But Simpson says drug addiction -- especially to crystal meth and crack -- may be a factor.

He says another contributing factor is likely a lack of social support for people who are homeless and resorting to staying in transit stations and stops.

Another underlying problem is poor access to mental-health services for the people who need it most.

The TTC has also said it's critical to address underlying social issues.

It is expanding an outreach program where workers offer shelter spaces to people who are homeless in transit stations.

This report by The Canadian Press was first published March 28, 2023.