Explanation:

Alright, here’s the rundown:

- Cannabis use: According to a recent SAMHSA study, kids ages 12 to 17 who use cannabis weekly are nearly four times more likely to engage in violent behavior.

- Opiates: These are less commonly used by teens and tend to be more linked to self-harm than external violence.

- Inhalants: While dangerous and damaging, there’s no strong link tying regular inhalant use to increased violence in this age group.

- Alcohol: Alcohol does increase risky behavior, but the SAMHSA study calls out cannabis specifically for this stat.

- Designer drugs: They're risky, sure, but again, not what the study is flagging in terms of violence.

So, the correct and specific answer is:

Option:1, cannabis