While all three can involve challenging behaviour, the motivations, severity, and associated features differ significantly.

1. Oppositional Defiant Disorder (ODD)
ODD is a behavioural disorder characterised by a consistent pattern of angry, irritable mood, argumentative/defiant behaviour, or vindictiveness toward authority figures.

Key Traits:
- Frequent temper tantrums
- Refusal to comply with requests or rules
- Deliberate attempts to annoy others
- Easily annoyed themselves
- Often blame others for their mistakes

Age of Onset:
 Typically before age 8, but diagnosis usually occurs by early adolescence.

Motivation:
Driven by emotional reactivity, frustration, or feeling out of control. Behaviour is often impulsive, not premeditated.

Severity:
 Milder than Conduct Disorder. Does not typically involve harm to others or animals.


2. Conduct Disorder (CD)
CD is a more severe disorder involving persistent patterns of behaviour where the rights of others or societal norms are violated.

Key Traits:
- Aggression toward people or animals (bullying, fighting, cruelty)
- Destruction of property
- Deceitfulness or theft
- Serious violations of rules (truancy, running away)

Age of Onset:
Childhood-onset (before age 10) or adolescent-onset.

Motivation:
Often calculated or goal oriented. Behaviour may be premeditated or manipulative. Empathy is typically lacking.

Severity:
More serious and long-lasting than ODD. Often requires multidisciplinary intervention.


3. Pathological Demand Avoidance (PDA)
PDA is a proposed subtype of autism spectrum disorder (ASD) marked by extreme avoidance of everyday demands and expectations, due to high anxiety.

Key Traits:
- Obsessive avoidance of demands (even ones they want to do)
- Use of socially manipulative behaviour (e.g. distraction, excuses, role-play)
- Surface sociability (appear social, but lack depth in interactions)
- Rapid mood changes and extreme reactions
- Comfort in role play or fantasy

Age of Onset:
Often noticed in early childhood.

Motivation:
 Avoidance is rooted in anxiety around loss of autonomy and perceived threats to control.

Severity:
 Can fluctuate with environment and support. Behaviour is driven by anxiety, not defiance or malice.

  • ODD = resisting because they want to oppose (control/anger/frustration).

  • PDA = resisting because they feel they can’t cope or fear the demand (anxiety-driven).