Bynes, 28, who was undergoing psychiatric treatment last year, had made headlines for her controversial Twitter posts in which she had slammed fellow celebrities and public figures, reported Ace Showbiz.
She was also arrested for allegedly throwing a bong out of her midtown apartment window.
"Amanda has no mental illness whatsoever. She has never been diagnosed as schizophrenic or bipolar. She is very sorry for all the hurtful tweets, statements and actions that occurred while she was under the influence of marijuana," Lynn released a statement via the family lawyer Tamar Arminak.
Her attorney claims that she kept mum all this while as Bynes thought it was the best thing to do.
"There has been much speculation about Amanda's medical condition. She has remained silent because she believed it was best to keep her mental health diagnosis private," Arminak said.
"However, she asked me to dispel certain rumours. For the record, Amanda does not have schizophrenia, nor has she ever been diagnosed with it," he added.