This mum's simple photo contains a powerful message about depression.

Our understanding of mental illness is ever evolving, as is our default image of someone with depression as a person weeping all day or with a permanent frown.

For US mum Brittany Ernsperger, who lives with depression and anxiety, the black dog is represented in a photo that might look innocuous to most, but is very telling of what depression truly is: a pile of clean dishes.

“This is what depression looks like,” The Relatable Mom blogger wrote in a Facebook post that has since been shared and liked by tens of thousands of people.

Brittany said it was not the fact the dishes were now clean, but that there were “that many dishes in the first place” and that she had gone two weeks without cleaning them.

In this insightful explanation of depression, the Indiana mum-of-four shared how simple tasks like cleaning the dishes, doing washing, taking a shower and even brushing her teeth can become unbearably daunting.

"Three days ago I sat on the kitchen floor and stared at [the dirty dishes] while I cried," she wrote.

"I knew they needed to be done. I wanted to do them so bad.

"But depression pulled me under. It sucked me in. Like a black hole. Rapidly, sinking quick-sand."

Her description of looking at the dishes, telling herself she would do them, "feeling defeated every day that I didn’t" and feeling like a failure because of it, is something many other sufferers related to.

"Man I can't count how many times this was me," wrote one Facebook user.

"Felt like I was reading my every thought," commented another.

Bestselling author Marian Keyes has lived with depression and speaks about it frankly in her No Filter chat with Mia Freedman. Post continues.

Brittany described her to-do list as a "nightmare" and shared what went through her mind every day.

"Worthless. Failure. Piece of shit. Incompetent. Stupid. Lazy. All things that roll through the mind of someone with depression. All. Day. Long."

She said she wanted to share the post as a message of encouragement to others.

"Depression is something that 'strong' people don’t talk about because they don’t want people to think they’re 'weak'," she wrote.

"You’re not weak. You’ve been strong for so long and through so many things, that your body needs a break.

"I don’t even care if the only thing you did today, was put deodorant on. I’m proud of you for it. Good job. I’m in your corner. I’m on your side."

Brittany said she was not looking for sympathy, just to let others know: "I'm here for you."