When someone is recovering from depression, family support is absolutely necessary.
うつ病の人が回復するには、家族の協力が必要不可欠だ - When someone is recovering from depression, family support is absolutely necessary もしくは When someone is recovering from depression the support of their family is really vital
When someone is recovering from depression - うつ病の人が回復している時
「協力」は英語で cooperation と言いますが、英語だと support (サポート, 支援, 援助) の方がこのトピックに合います。
必要不可欠 - absolutely necessary, vital