The GP was comparing cocaine to (substituted) amphetamines, which as with most dopaminergic psychostimulants also cause addiction via changes to ΔFosB expressio

The GP was comparing cocaine to (substituted) amphetamines, which as with most dopaminergic psychostimulants also cause addiction via changes to ΔFosB expression. Hence, I'd say the comparison isn't incorrect, even if the GP's appraisal of the potential harm of speed/ecstasy may have been understated. However, ΔFosB expression is also impacted by all kinds of behaviors and substances, including palatable/calorie-dense foods, exercise, and sex. There's a lot of things that alter brain chemistry in the long term if abused.