Mental
Emotional, Spiritual
な adjective
Your 精神 is your spirit or your mind. If you add 的 to it, you get mental. It can mean spiritual too, but it more often shows up in reference to a person's mental or emotional state.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
精神的に病んでいた時、毎日一人で公園をブラブラしていました。
When I was mentally troubled, I was wandering aimlessly around the park alone every day.