LSD works by reducing your sense of self (or ego, if you will).
This works by the drug interfering with the functional connectivity in the brain, which increases communication between brain regions (including those which typically are not very well-connected) (Liechti, 2017). In particular, the serotonin receptors 5-HT2A and 5-HT2BR show abnormal activation by LSD, thus causing visual hallucinations (Schmidt et al., 2018; Wacker et al., 2017). Neuroimaging studies have shown that the brains on LSD mimic brains of those with psychiatric disorders, such as schizophrenia. These findings are in fact so similar, that researchers are currently using these models in order to treat schizophrenia. This is done by using a 5-HT2A receptor antagonist, with the antagonist preventing the patient's hallucinations. (Preller et al., 2016; Halberstadt, 2017).
Psilocybin (mushrooms) also alter your sense of self and causes visual hallucinations by increasing activation of the same serotonin receptor 5-HT2A.
Does this mean LSD or other psychedelics cause disorders such as schizophrenia?
No.
But it means that anyone with a real risk of developing a psychiatric disorder (or is already diagnosed with one) such as schizophrenia should approach psychedelics cautiously as these drugs activate the very receptor(s) (5-HT2A) which appear to cause their hallucinations!
I am well aware of the fear-mongering and false information that was all the rage in the 60s and onwards.
Unfortunately, it has meant that scientific endeavours to research these substances (LSD, MDMA, psilocybin, cannabis etc) has been incredibly difficult. Only in the last few years have researchers been allowed to study the effect these drugs have on the brain. Hence, it is also difficult to give definite answers on their properties as there is simply a lack of replicated studies.
I suggest you take a look at the studies done by researchers at the Imperial Psychedelic Research Group, if you haven’t already.
I am not denying that psychedelics or other substances may have therapeutic use. However, it is irresponsible to only promote their potentially positive effects while ignoring the risks that they pose. This is particularly true for those who have a risk of, or already have, very real and life-changing psychiatric disorders.
Off-topic
Although I release this topic is not about drug interactions, I thought it might be useful to leave a note on MDMA, psychadelics, and anti-depressants. I imagine there may be a few of you who on here who are on medication and are thinking about trying to give psychadelics or MDMA a go.
MDMA work differently by affecting your serotonin. Simply speaking, serotonin is the ’happy’ chemical your body produces in order to keep your mood stable. MDMA reduces your sense of fear and increases empathy. It does this by releasing all the serotonin that are currently held in your cells. MDMA should not be taken together with MAOI medications (used for depression) as they may cause serotonin syndrome, in which the person presents with symptoms such as tremors and high body temperature.
Furthermore, excessive use of MDMA can severely deplete the body of its serotonin reserves. On studies on monkeys, this depletion has shown to take a year or several years before the body is once more able to produce sufficient levels of serotonin (Taffe et al., 2002; Ma et al., 2016).
Anyone on SSRIs (anti-depressants such as prozac or zoloft) is pretty much unable to feel any effects of psychadelics or MDMA, although it is not considered dangerous to take them together. This is because the SSRIs distribute serotonin in your body, which is then absorbed by your cells . SSRIs also further inhibit your cells' ability to reabsorb, stabilizing your mood. Hence, psychadelics and MDMA which rely on affecting the serotonin receptors (5-HT) in your cells are blocked by the SSRIs.
TL;DR: Don't waste your money on psychadelics or MDMA if you're on anti-depressants. If you have a family history of psychiatric disorders, i.e. schizophrenia, stay away from psychadelics.
References
_____Halberstadt, A. L. (2017). Hallucinogenic drugs: A new study answers old questions about LSD. Current Biology, 27(4), R156-R158.
_____Ma, K. H., Liu, T. T., Weng, S. J., Chen, C. F. F., Huang, Y. S., Chueh, S. H., ... & Huang, W. S. (2016). Effects of dextromethorphan on MDMA-induced serotonergic aberration in the brains of non-human primates using [123 I]-ADAM/SPECT. Scientific reports, 6, 38695.
_____Preller, K. H., Herdener, M., Pokorny, T., Planzer, A., Kraehenmann, R., Stämpfli, P., ... & Vollenweider, F. X. (2016). The role of the serotonin 2A receptor in the fabric and modulation of personal meaning in lysergic acid diethylamide (LSD)-induced states. European Neuropsychopharmacology, 2(26), S299-S300.
_____Schmidt, A., Müller, F., Lenz, C., Dolder, P. C., Schmid, Y., Zanchi, D., ... & Borgwardt, S. (2018). Acute LSD effects on response inhibition neural networks. Psychological medicine, 48(9), 1464-1473.
_____Taffe, M. A., Davis, S. A., Yuan, J., Schroeder, R., Hatzidimitriou, G., Parsons, L. H., ... & Gold, L. H. (2002). Cognitive performance of MDMA-treated rhesus monkeys: sensitivity to serotonergic challenge. Neuropsychopharmacology, 27(6), 993.
_____Wacker, D., Wang, S., McCorvy, J. D., Betz, R. M., Venkatakrishnan, A. J., Levit, A., ... & Shoichet, B. K. (2017). Crystal structure of an LSD-bound human serotonin receptor. Cell, 168(3), 377-389.