Research
What research establishes
Peer-reviewed work confirms that brumation in Pogona vitticeps involves substantial physiological and gene-expression changes. It is a real seasonal state.
The research does not establish a universal minimum age for captive brumation. Blanket claims that juveniles cannot brumate are therefore stronger than the evidence.
Evidence limit
What still requires caution
Reduced activity in a young dragon can also reflect inadequate temperatures, poor nutrition, parasites or illness. Age alone cannot tell those possibilities apart.
A juvenile should not simply be assumed to be brumating when weight, condition or behaviour is concerning. Seasonal behaviour must be interpreted alongside health and husbandry.