It is often stated serious metal illness if not treated can harm the brain development. What basis is there for this? Are there verifiable tests for such?
Example for this:
Usually, when we think “brain changes” we think it means something bad, like damage or stunting. But it’s important to remember that untreated mental illness can also harm brain development. Early medication can help prevent the illness from getting worse or becoming neurally entrenched.
Scientific America: Should Kids Take Psychiatric Medication?
It should be stated often antipsychotics(common treatment for bipolar) result in brain damage if you measure gray matter in animal and human subjects between those that take them and those that don't.