Low serotonin levels are also linked to a host of psychiatric afflictions other than impulsive aggression. Some of these include migraines, pathological shyness, obsessive-compulsive disorder, anxiety, restless leg syndrome, gambling, and depression, besides several addictions (food, sex, and drugs).
Selective serotonin reuptake inhibitors are among the most widely prescribed drugs, being consumed by millions upon millions, most commonly for depression, but also many of these other disorders. Unless the data is deeply misleading, the alternative explanation is that serotonin shortage is linked to a plethora of behavioral-emotional problems, and not merely aggression.
This is plausible, given that serotonin-producing neuron in the brainstem network with many different parts of the brain, including a broad range of functions.
Therefore, rather than linking serotonin to aggression specifically, it is wiser to assume that this neurotransmitter underlies many psychiatric conditions and neurobiological processes.
And even more important, it shows that neurobiology cannot explain the steep rise in violent and aggressive behavior in the US, for instance, but this can be imputed with far more justice to social, cultural and economic causes that promote violent behavior.
Perhaps serotonin levels may be one of the genetic causes that predispose to the adoption of aggressive behavior, but nothing more.