"By building understanding I think we can get away from the idea that mental illness in young people is primarily a moral problem or a random disaster and try and move understanding more toward a rational direction, " said Prof Bullmore.

BBC: Brain scan study to understand workings of teenage mind

The employee who handled the letter has no symptoms of illness, and there's no reason to believe any employees are at risk from being in the building where it was delivered, the mayor's office memo said Thursday.

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