The Bible does not specifically address the topic of mental health; but, it does have a great deal to say about the heart and mind, spiritual brokenness, and the condition of the soul, among other things. Because it impacts the entire self, mental health is critical: "Above all else, guard your heart, for everything you do flows from it" (Proverbs 4:23).
The world has reached a point of no return (Genesis 3). We are separated from God because of sin (Isaiah 59:2), and creation is corrupted as it cries out for deliverance from its state of decay (Romans 8:21–22). Because of the fall of mankind, there have been physical ramifications for the body as well as spiritual ramifications for the soul. Mental health is not guaranteed in the same way that physical health is, and the mind, like the body, can become ill or damaged at any time.
There are numerous verses in the Bible that talk indirectly to mental health. According to Romans 12:2, it is the Lord who renews the mind, and it is He who restores the soul (Psalm 23:3). God has given His children "a spirit that is not afraid, but one that is full of strength, love, and self-control" (2 Timothy 1:7, ESV). In John 14:27, Jesus promises us that we will be at peace and will be able to rest (Matthew 11:28). There are also several scriptural injunctions to "fear not" and to "present our anxieties to God," among other things (Isaiah 41:10; Matthew 6:34; Philippians 4:6; 1 Peter 5:7).
The health of the mind is intertwined with the health of the body and the health of the spirit. With Elijah's mental health having deteriorated throughout his fight with Queen Jezebel, we might draw inspiration from the biblical story. Elijah escaped the country and sought refuge in a remote location where he hoped to die (1 Kings 19:4). In the first place, God attended to Elijah's physical needs, supplying him with food and providing him with time to sleep (verses 5–6). God knew that his travel would be "too much" for him at this point in his life (verse 7). The Bible says that when Elijah had rested and refueled physically, God provided him with encouragement, a new mission, and an assistance (verses 15–18).
Jonah is an example of a person whose mental health was negatively impacted by poor decisions he made. After God spared Nineveh, Jonah expressed a desire for death (Jonah 4:3), a desire that is highly symptomatic of a melancholy mood. The disobedience against God by Jonah served as a prelude to this. Despite the fact that he had directly disobeyed the Lord's instruction (Jonah 1:1–3), his heart remained out of sync with God's desires even after God brought him back into line. Rather than marveling at God's kindness and worshipping Him for His grace, Jonah wished to perish rather than live. The only way Jonah's sadness could ever be alleviated was through a reconnection with God.