'Sister Wives' Garrison Brown's Sibling Says Social Media Hurt Self-Esteem

Garrison Brown was negatively affected by social media before his death -- and it impacted his own sense of self-worth ... this according to one of his siblings.

The "Sister Wives" star's actual sister, Madison Brown Brush, hopped online to post an emotional video reflecting on her brother's untimely passing -- and she spoke a lot about his mental health struggles, while also acknowledging pointing to mental health convos at large.

Maddie explains her brother was battling issues internally -- and even says he felt he wasn't doing enough with his life ... using social media as a comparison point.

She also says something pretty poignant ... namely, social media isn't real.

Maddie goes on to explain how she and the rest of the family have been dealing with Garrison's suicide -- describing how difficult it's been finding a new sense of normal.

She urged her followers to remember that social media is just a snapshot into someone's life -- it doesn't show everything. Remember, Garrison's loved ones say he seemed perfectly happy online ... having just adopted a new cat days before he died by suicide.

Maddie goes on to say that she's going to continue putting a spotlight on mental health ... and sends a message to people who might be battling demons -- telling them that if they're not feeling fulfilled with how they're spending their time, they gotta change that ASAP.

We broke the story ... Garrison was found deceased in his Flagstaff, Arizona home earlier in March. Flagstaff PD told us that no foul play is suspected, as Garrison appeared to have suffered from a self-inflicted gunshot wound.

He was only 25.