Sure, here is a possible ontology for the study of mental health and cognitive processes, including ADHD, anxiety, and preterm birth:

Mental health and cognitive processes
- ADHD
- Anxiety
- Preterm birth
- Brain structure and function
- Psychological theories and models
- Neural basis of behavior and cognition
- Environmental factors
- Genetic factors
- Interventions
Brain structure and function
- Neurons
- Glial cells
- Brain regions
  - Cortex
  - Hippocampus
  - Cerebellum
  - Basal ganglia
  - Thalamus
  - Amygdala
  - Prefrontal cortex
  - Anterior cingulate cortex
- Neurotransmitters
  - Dopamine
  - Serotonin
  - GABA
  - Glutamate
Psychological theories and models
- Attention
  - Attention deficit/hyperactivity disorder (ADHD)
  - Attention network test
- Memory
  - Atkinson-Shiffrin memory model
  - Dual-store memory model
  - Working memory
- Learning
  - Classical conditioning
  - Operant conditioning
  - Observational learning
- Emotion
  - Affective consciousness
  - Dimensional and primary process emotion approaches
Neural basis of behavior and cognition
- Neural circuits
- Neural plasticity
- Neural oscillations