The antidepressant compounds are compounds of the formula: wherein R1 and R2 are either both hydrogen or both halogen (particularly chlorine), and if R1 and R2 are both hydrogen, R3 and R4 are both halogen (particularly chlorine), otherwise both R3 and R4 are hydrogen; or a pharmaceutically acceptable salt thereof. The compounds may be prepared by: (a) reducing 1,8-dihaloanthrquinone with zinc powder in aqueous ammonia, followed by acidic treatment to provide 1,8-dihaloanthracene; (b) Diels-Alder [4+2] cycloaddition reaction of the 1,8-dihaloanthracene and acrolein at room temperature in the presence of boron trifluoride etherate to obtain a mixture of the intermediate compounds 1,8-dihalo-9,10-dihydo-9,10-ethanoanthracene-11-carbaldehyde and 4,5-dihalo-9,10-dihydo-9,10-ethanoanthracene-11-carbaldehyde; (c) separating the mixture of carbaldehydes by column chromatography; and (d) direct reductive amination of the respective carbaldehydes to obtain the corresponding antidepressant compounds of the above formula.