The honest short answer is more nuanced than either extreme you may read online
It's a catastrophic failure at the molecular level
(PDF) Harnett, N.G., Finegold, K.E., Lebois, L.A.M., van Rooij, S.J.H., Ely, T.D., Murty, V.P., Jovanovic, T., Bruce, S.E., House, S.L., Beaudoin, F.L., An, X., Zeng, D., Neylan, T.C., Clifford, G.D., Linnstaedt, S.D., Germine, L.T., Bollen, K.E., Rauch, S.L., Haran, J.P., Storrow, A.B., Lewandowski, C., Musey, P.I., Hendry, P.L., Sheikh, S., Jones, C.W., Punches, B.E., Kurz, M.C., Swor, R.A., Hudak, L.A., Pascual, J.L., Seamon, M.J., Harris, E., Chang, A.M., Pearson, C., Peak, D.A., Domeier, R.M., Rathlev, N.K., ONeil, B.J., Sergot, P., Sanchez, L.D., Miller, M.W., Pietrzak, R.H., Joormann, J., Barch, D.M., Pizzagalli, D.A., Sheridan
Prioritize quality sleep to help your mind recharge, stay well-hydrated to maintain focus and mental energy, and take regular breaks from screens to reset and protect your attention span