godan verb (-mu), intransitive verb
suffer; be in pain; struggle; be troubled
Broad intransitive verb for physical or mental suffering, distress, or hardship. Often used with ～に苦しむ (suffer from something) or ～で苦しむ (suffer due to something).
彼は長い間、病気に苦しんでいる。
He has been suffering from illness for a long time.
不景気で多くの企業が苦しんでいる。
Many companies are struggling due to the recession.
彼女は人間関係に苦しんでいた。
She was troubled by her relationships.