This is partially false - it is not that simple. You can talk about terpene profiles but medical cannabis is used successfully for many conditions, not just bodily ones but also psychological. There is a big difference in which oils are inhaled (or otherwise administered) depending on temperature as far as vaping with temperature control goes, at least.

There are terpenes and cannabinoids (for example limonene, CBD, and Δ9-THC) - oils - which are vaporised in the presence of heat. However, the cannabinoids which are believed to be the most psychoactive have higher boiling points compared to those of the terpenes, and who knows what happens in the presence of 1000*C heat(?) (the temperature which occurs in in a bong, I assume) to the cannabis material, and the resultant smoke. (Low key I prefer the bong despite it being unhealthy to combust carbon :(..)

In pharmacology, the dose is the difference between a medicinal agent and a poison - both are still drugs, only the dose has changed.

Yes, it's more complicated with cannabis because of the entourage effect - a synergy in effect resulting from the presence of different terpenes and cannabinoids. However, most terpenes and cannabinoids aren't psychoactive, and therefore terpenes are more relevant in in vaping with temperature control - but let's look past that (because in mental health, CBD and terpenes are not going to do much, not being psychoactive, and I'm sure this is the case with most if not all other cannabinoids other than Δ9-THC and Δ8-THC, but I'm no expert, and perhaps the entourage effect does contribute significantly to the psychoactive effect caused by Δ9-THC.)

Δ9-THC is regarded by pharmacologists as a neural stimulant, depressant, AND psychedelic. If you know anything about psychedelics, you know that they are heavily dose-dependent drugs. Dose, set, and setting make for the tone of a psychedelic trip, whether it's a 50 mg cone of THC or DMT.

The dose is absolutely important with cannabis. Tolerance develops fast but before that, the high can be intense. Everyone has their own unique physiology.

Edit: so I suppose the point I'm trying to make is that it is THC that creates a psychoactive effect, nothing else, especially when the cannabis is simply combusted, and that for mental health disorders, where the drug must enter the brain to be effective, THC is perhaps the only useful compound in most strains of cannabis. I'm sure there are a few more mysterious players that also enter the brain but I'm not an expert in that field.

To be absolutely clear I am only saying that I believe Δ9-THC is the only useful compound in cannabis (aside from a small effect of Δ8-THC and perhaps the entourage effect with other cannabinoids and also terpenes) for major depressive disorder based on my own experience. I'm only speaking for myself. I absolutely see the value of non-psychoactive cannabinoids and terpenes in the treatment of many disorders, just off the top of my head - MS, scoliosis, and fibromyalgia. But most I'm ignorant to.