I remember correctly because I didn't get cognitive side effects on Lithium, but it did kill my thyroid function, and it is permanent damage - when I was off Lithium, I still needed to take Synthroid. Without Synthroid, I could not get up. At all - extreme fatigue without any depressive thoughts. Thought pattern was more like:"oh, how curious it is that I cannot even lift my finger. Funny, no?"

so I was put back on Synthroid when I was off Lithium. That makes the side effect tardive. Your gap in memory is tardive, too. Yet when you read the list of possible side effects, you don't see "and can become tardive" in large red print, do you?