The 37-year-old Briton assured fans on Instagram that they were not alone.
“It’s been such a tough year already with everything that is happening around us,” Hamilton said.
“I have struggled mentally and emotionally for a long time, to keep going is a constant effort but we have to keep fighting, we have so much to do and to achieve.
“I’m writing to tell you it’s OK to feel the way you do, just know that you are not alone and we are gonna get through this.”
Hamilton missed out on a record eighth championship last year after a controversial final race of the season in Abu Dhabi that he had led until the last lap.
The sport’s most successful driver of all time, with a record 103 wins and poles, shunned social media from the day of that December race until February.
His silence fuelled speculation surrounding his future, with Mercedes team boss Toto Wolff describing Hamilton as “disillusioned”.
The sport’s only Black driver, an outspoken champion for equal opportunities and diversity, Hamilton has also experienced racism and online abuse.
The Briton has had a difficult start to his 16th season, finishing only 10th in Saudi Arabia last weekend after failing to get through the first phase of qualifying in a car that has been off the pace.