Anxiety can mimic symptoms of bipolar disorder. Anxiety disorders are common in children, and they trigger changes in mood and behavior that can look like manic or depressive symptoms. Anxiety disorders cause fear and distress that are out of proportion to any actual threat.
The fear and distress then trigger behavioral responses to try to reduce the threat, typically in one of two forms — fight or flight. Fight looks angry and out of control — the brain trying to save itself from a perceived danger. Flight can include running away from something, but can also present as avoidance and refusals and shutting down. Anxiety can mimic symptoms of bipolar disorder in some of the following ways:
Irritability: Fear triggers a need to control the environment, to reduce threats, and to keep things safe. When the world doesn't cooperate (if children must do things that trigger fear or must stop doing something that is helping them stay calm), they can become angry and sometimes explosive. This behavior looks like the mood dysregulation found in mania and depression.
Racing thoughts: Anxious people's brains are always scanning the environment for threats and are very busy worrying about potential dangers. This often presents as a subjective sensation of racing thoughts, also a symptom of mania.
Demanding and controlling behaviors: People with anxiety work hard to control their environments. Parents are tasked with getting children to do things they don't want to do, which can be particularly difficult with anxious children, leading to hours of struggle with escalating tempers and mood changes.
Oppositional/defiant behaviors: The flight response of anxiety can present as refusals and shutting down when given demands that trigger anxiety or distress. When the adult escalates the demands and becomes firmer (or even angry), the child's anxiety escalates, creating further paralysis and even less likelihood of meeting the adult's demand. This can easily turn into angry or sobbing outbursts that look like a mood disorder.
Obsessive compulsive disorder (OCD) isn't technically an anxiety disorder, but is related. Children with OCD have repeated and out-of-the-ordinary fears (for example, that the doors are unlocked and a stranger will come in and hurt them) that they control with a variety of mental or physical rituals and behaviors (for example, checking door locks over and over before being able to sleep).
If people with OCD aren't allowed to perform their behaviors, their level of distress can escalate dramatically and quickly. It can present as irritability with explosive mood and behaviors that are puzzling to parents and teachers and that look like mania or depression. Kids often can't or won't communicate their fears, which can make OCD difficult to diagnose. Your child's doctor should consider OCD, if your child has explosive outbursts.