Complex sentence: As for the cause and effect of happiness or unhappiness, the research was not conclusive, in some cases, optimism appears to be the effect not the cause of well-being and in other cases it appears to be the cause.
Split into simpler sentences: As for the cause and effect of happiness or unhappiness, the research was not conclusive. In some cases, optimism appears to be the effect not the cause of well-being and in other cases it appears to be the cause.