Self-relationships through pivot tables

User.php

<?php

namespace App;

use Illuminate\Notifications\Notifiable;
use Illuminate\Foundation\Auth\User as Authenticatable;

class User extends Authenticatable
{
    use Notifiable;

    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'name', 'email', 'password',
    ];

    /**
     * The attributes that should be hidden for arrays.
     *
     * @var array
     */
    protected $hidden = [
        'password', 'remember_token',
    ];

    /*
     * Users who this user is a doctor
     */
    public function patients()
    {
        return $this->belongsToMany(
            User::class,
            'user_relationships',
            'doctor_id',
            'patient_id'
        );
    }

    /*
     * Users who are doctors of this user
     */
    public function doctors()
    {
        return $this->belongsToMany(
            User::class,
            'user_relationships',
            'patient_id',
            'doctor_id'
        );
    }

    /*
     * All users who are doctors
     */
    public function scopeFilterByDoctors($query)
    {
        $query->has('patients');
    }

    /*
     * All users who are patients
     */
    public function scopeFilterByPatients($query)
    {
        $query->has('doctors');
    }
}

// All users who are doctors
User::filterByDoctors()->get();

// All users who are patients
User::filterByPatients()->get();

// Patients of a given user
User::find($id)->patients()->get();

// Doctors of a given user
User::find($id)->doctors()->get();