When a Child Changes Overnight – Understanding PANS/PANDAS and Behaviour
AnneMarie Smellie is a UK-based neurodevelopmental practitioner, kinesiologist, and hypnotherapist with over 20 years’ experience helping children and adults build resilience, regulate anxiety, and strengthen brain–body foundations for learning and life.
Parents often describe it the same way, "It was like my child disappeared." A child who was once emotionally steady suddenly becomes anxious, rigid, aggressive, withdrawn, or obsessive. Meltdowns escalate. Sleep deteriorates. Separation anxiety appears out of nowhere. School refusal follows. And no one can quite explain why.
When behavior shifts rapidly and dramatically, it is not a parenting failure, and it is rarely "just a phase."
For some children, these changes are driven by a little-known but profoundly impactful condition: PANS/PANDAS.
What are PANS and PANDAS?
PANS (Pediatric Acute-onset Neuropsychiatric Syndrome) and PANDAS (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections) describe a sudden inflammatory response in the brain following infection or immune activation.
In simple terms, the immune system becomes confused and begins attacking areas of the brain involved in:
Emotional regulation
Behavior
Motor control
Executive functioning
This is not psychological in origin, it is neurological and immunological.
The key feature that distinguishes PANS/PANDAS from other developmental or emotional difficulties is acute onset. Parents often pinpoint a specific moment in time when everything changed.
How PANS/PANDAS can shape behavior
Because inflammation affects the brain, behavior becomes the outward expression of an internal biological storm.
Children may show:
Sudden, intense anxiety or panic
Obsessive thoughts or compulsive behaviors
Rage episodes that feel "out of character"
Extreme emotional volatility
Regression in speech, learning, or independence
Sensory sensitivities to sound, light, or touch
Tics or changes in movement
Sleep disruption and fatigue
Importantly, these behaviors are not willful. The child is not being defiant or manipulative. Their nervous system is overwhelmed, and their brain is struggling to process information safely.
From the child’s perspective, the world has become unpredictable and threatening.
Why PANS/PANDAS is so often missed
Many children with PANS/PANDAS are initially labeled with:
Anxiety disorders
OCD
ADHD
Behavioral difficulties
Autism-like traits
While these labels may describe what is seen, they do not explain why the behavior appeared so suddenly.
If we only address behavior through rewards, consequences, or talking therapies, without addressing inflammation and nervous system dysregulation, children often worsen rather than improve.
Behavior is communication. In PANS/PANDAS, the message is clear, "My brain is under attack, and I don’t feel safe."
The nervous system connection
One of the most overlooked aspects of PANS/PANDAS is the state of the nervous system. Children in this condition are often stuck in:
Fight (rage, aggression)
Flight (avoidance, panic)
Freeze (withdrawal, shutdown)
Expecting emotional regulation from a nervous system locked in survival mode is unrealistic. Until the body feels safer, behavior will remain dysregulated, no matter how much logic or reassurance is offered.
Why a whole-child approach matters
Supporting a child with suspected PANS/PANDAS requires looking beyond symptoms. Key areas to consider include:
Immune triggers (including recurrent infections)
Inflammation and detoxification pathways
Nutritional deficiencies that affect brain function
Sensory processing and auditory overload
Retained primitive reflexes that keep the nervous system on high alert
Emotional stressors that may amplify immune responses
No two children present in exactly the same way, which is why a one-size-fits-all approach rarely works.
Progress comes from reducing the load on the system, not demanding more from the child.
What parents need to hear
Perhaps the most important message is this: Your child is not broken. Your parenting has not failed. Their behavior is a signal, not a character flaw.
When inflammation is addressed, the nervous system is supported, and the child’s foundations are strengthened, many families begin to see glimpses of the child they remember, sometimes quite quickly, sometimes gradually.
Hope does not come from forcing change. It comes from understanding what the body is asking for.
A final thought
Children do well when they can. When they cannot, we must ask better questions.
PANS/PANDAS invites us to move away from blaming the child, the parent, or even ourselves, and towards curiosity, compassion, and informed support. And sometimes, that shift alone changes everything.
Read more from AnneMarie Smellie
AnneMarie Smellie, Neurodevelopmental Practitioner, Kinesiologist, and Hypnotherapist
AnneMarie Smellie is a UK-based neurodevelopmental practitioner, kinesiologist, and hypnotherapist with over 20 years of clinical experience. She specialises in anxiety, neurodiversity and learning differences, working at the intersection of brain development, nervous-system regulation and emotional resilience. Through her work at Quester Therapies, AnneMarie helps children and adults uncover and address the root causes behind behavioural, emotional, and cognitive challenges. Her writing focuses on practical, compassionate insights that make complex brain-body concepts accessible and empowering.
