This line of reasoning involves the "chicken or the egg" hypothesis, which is a classic example of a causal dilemma. In this case, the dilemma is whether smiling causes happiness or whether happiness causes smiling.
There is evidence to support both sides of the argument. On the one hand, some research suggests that smiling can have a positive effect on an individual's mood and can contribute to feelings of happiness. Smiling can release endorphins, which are chemicals that can help to reduce stress and improve mood. Additionally, smiling can be contagious and can lead to positive social interactions and relationships, which can contribute to feelings of happiness.
On the other hand, other research suggests that happiness can also cause smiling. When people are happy, they may naturally smile more often as a way to express their feelings. In this case, the smile is a result of the happiness rather than the cause.
Overall, it is likely that both smiling and happiness can influence each other in a feedback loop, with each contributing to the other. It is difficult to determine which comes first in any given situation, and it may vary from person to person.