I think there are a lot of statistical studies that show a strong correlation between meth and violence.
However, use of the drug also alters normal function in a specific part of the limbic system that processes emotions such as anger and fear. As a result of this alteration, people using methamphetamine can easily develop paranoid, aggressive, or violent states of mind.
Together with decreased behavioral control inside the pre-frontal cortex, the presence of anxiety, fear, terror or panic set the stage for unpredictable episodes of aggression and violence in habitual meth users. The potential for these behaviors is also tied to the onset of a disorder called methamphetamine-induced psychosis. People with this disorder develop psychotic symptoms that can include auditory (sound-based) or visual hallucinations, as well as various forms of delusional thinking. In some cases, this delusional thinking involves paranoid fixations, and people in the grips of psychosis have a clear capacity to turn aggressive or violent.
https://www.elementsbehavioralhealt...en-methamphetamine-use-paranoia-and-violence/
Data were collected from extensive interviews of 350 methamphetamine users who received substance use treatment in a large California county. A majority (56%) perceived that their methamphetamine use resulted in violent behavior; 59% reported specific violent criminal behaviors. For more than half of those reporting violent criminal behavior, this behavior pattern began before methamphetamine initiation. Thus, for a subsample of methamphetamine users, violence may be related to factors other than methamphetamine use. Users’ perceptions that their methamphetamine use resulted in violence appears strongest for those with the most severe methamphetamine-related problems, particularly paranoia.
http://www.antoniocasella.eu/archipsy/Brecht_2013.pdf
The number of murders and armed robberies committed by people addicted to methamphetamine is "truly frightening", Western Australia's Chief Justice says.
Justice Wayne Martin said 95 per cent of armed robberies and up to half of all murders could be attributed to people taking methamphetamine, also known as ice or crystal meth.
http://www.abc.net.au/news/2015-02-25/wa-chief-justice-says-ice-problem-truly-frightening/6261310
