"What product and dosage?"
Hi there! Serotonin is one of two major neurotransmitters (GABA being the other) responsible for anxiety relief. In fact, restoring activity in serotonin pathways—by increasing the serotonin available to bind a subtype of the serotonin receptor (5-HT1A) in the brain—is how SSRIs (Selective Serotonin Reuptake Inhibitors) are thought to alleviate anxiety and depression.
Similarly, several recently published studies suggest that CBD does the same. However, it does so, not by increasing the serotonin available to bind 5-HT1A receptors, as SSRIs do, but by mimicking serotonin's action at the 5-HT1A receptor; or, in scientific terms: CBD is a 5-HT1A receptor agonist. https://www.ncbi.nlm.nih.gov/pubmed/16258853 https://www.ncbi.nlm.nih.gov/pubmed/24923339
In two 2018 studies, researchers administered CBD to rats, which then resulted in significant reductions in anxiety- and depression-related behaviors. However, when the rats were pre-treated with an agent that blocks the 5-HT1A receptor, CBD did not affect their behaviors, thus indicating that CBD's interaction with the 5-HT1A receptor was the affecting mechanism. https://www.ncbi.nlm.nih.gov/pubmed/30157131 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2697769/
Additionally, several studies suggest that CBD's interaction with the 5-HT1A receptor is the mechanism of action responsible for neuropathic pain relief, and the reduction of OCD and addiction-withrawal symptoms.
I hope this helps!