Complex sentence: What differentiates oniomania from healthy shopping is the compulsive, destructive and chronic nature of the buying; where shopping can be a positive root to self-expression, in excess it represents a dangerous threat.
Split into simpler sentences: What differentiates oniomania from healthy shopping is the compulsive, destructive and chronic nature of the buying. Where shopping can be a positive root to self-expression, in excess it represents a dangerous threat.